Growing Under Glass

Types of greenhouses and frames 1

Greenhouses vary greatly in size, shape and up by paths, doors and equipment such as Shapes and styles styles have come on to the market. These
type to meet the widely different demands of heaters and water tanks. The second way of Greenhouses are either free-standing or lean- usually have flat oblong wall panels but some
gardeners. This wide choice is not always calculating space is to consider the growing to, that is, supported on one side by a house also are geodesic in structure, miniature
helpful to the beginner, who is often thor- area in conjunction with the height at the or other wall. Free-standing houses may have versions of the vast space-dome-like Clima-
oughly confused by the variety of shapes and eaves and the height at the ridge. These two straight or inward sloping walls. Roof shapes tron greenhouse at the Missouri Botanic
materials. The basic factors which must be dimensions affect first the amount of grow- may be a simple span, hipped or double- Garden. Some of the more recent designs
considered are what the greenhouse is to be ing space for tall plants, such as tomatoes, hipped curvilinear. The "mini" lean-to is a have curved glass panels and an overall shape
used for, the amount of money available, and shrubs and climbers, and second ease of structure much narrower than the usual lean- that suggests the great Palm House at Kew
where the greenhouse is to be erected. access and comfort in use. In general, the to greenhouse. They are useful for the small Gardens in London. Certain circular styles
larger the greenhouse the cheaper each unit garden or where wall space is at a premium. have decided aesthetic appeal and can be-
When buying a greenhouse, carefully of growing space becomes, though this is less The smallest ones are too narrow to enter and come a feature or focal point in the garden.
assess the amount of growing space required. apparent in those models where the walls maintenance of the plants is done from the In addition they contain a surprising amount
There are two ways of measuring growing slope inwards. All too often the beginner outside. On sunny walls overheating can be a of space, as the central path of a traditional
space. The first is a simple calculation of the chooses a greenhouse which in time proves problem in summer. oblong structure is done away with. At
soil or bench area available, which tells how to be too small. If cost dictates a small green- present however, they are more expensive in
many plants may be accommodated. Simply house to start with, make sure it is a model to During recent years greenhouse manufac- terms of growing space than structures of
multiply the length of the greenhouse by the which extra sections can be added. turers have been seeking more original de- traditional shape.
breadth, taking account of the space taken signs, and as a result circular and domed

Types of greenhouses and frames 2

Another departure from the traditional tages, and the choice must depend upon the The crucial factors in the choice of shape Mobile greenhouses
greenhouse is the use of a framework of use to which the greenhouse is to be put. If are accessibility, light transmission, and sta- Commercial growers use mobile greenhouses
tubular alloy or steel supporting a cover made crops are to be grown in the border, glass to bility and durability. Commercially-available of the Dutch light type, which can be pulled
of plastic sheeting. Early models, still much ground is needed for light. If most plants will greenhouses can be expected to be stable, on a system of rails over crops. These allow a
used commercially, are called tunnel houses. be grown in pots, a staging is essential and the though the site must be taken into account in crop rotation program to be followed. For
Smaller versions of this simple pattern are wall area beneath it can be made solid. Brick, choosing a design. Plastic-covered houses, example, salad crops can be started on one
available for the amateur, and welded frame- wood or asbestos-cement half walls provide for instance, are less durable in very windy site in spring, then left to mature in the open
works in a variety of shapes are made. useful insulation, cutting the heating require- places. Accessibility covers factors such as while the house is moved onto a new site
Generally these have a traditional outline but ments of the greenhouse. A compromise is door design, which is dealt with on page 9, where tomatoes are grown.
some are dome-shaped. Plastic houses are to board the north wall only, gaining some and heights at eaves and ridge pole. Low-
cheaper than glass-clad ones but have draw- insulation with little effect on light values. built houses can be raised on a home-made Frames
backs in use (see pages 10 and 11). plinth of brick, wood or concrete to give It is less easy to vary the overall design of a
Removable wooden insulation panels are extra headroom. Light transmission is critical garden frame and the basic traditional shape
Design made for some designs of greenhouse. These only in winter and early spring, for during the is still frequently met with. This is a shallow
Greenhouses can be fully glazed, or they can can be fitted in winter and removed when summer months more light is available than oblong box with one end higher than the
have one or more sides boarded or bricked crops are to be grown in the bed. Kick boards is needed by the plants. Thus light is only of other and sloping sides shaped to hold a lid
up to staging height. Both styles have advan- should be fitted at the base of glass-to-ground concern when planning very early crops. or light of glass or plastic. A useful size is
walls to protect against accidental damage.

Types of greenhouses and frames 3

4 x 6 ft. Double and multiple frames of this Cloches The traditional cloche (a) was made of solid anchored with wire hoops. Plastic tunnel
design can be obtained. Variations include glass in a bell form. Class sheets joined cloches (e) consist of long plastic sheets
double span tops and glass walls with a Until comparatively recently, cloches were with clips can be tent-shaped (b) or barn- bent over hoops and held with more
number of different patented methods of made as units or sections, each one like an shaped (c). Corrugated plastic sheeting (d) hoops. Plastic sheet attached to wire
opening. open-ended greenhouse in miniature, fitting can be bent over rows of crops and frames forms a tent cloche (f).
together to cover rows of crop plants. Made
Light-weight metal or plastic frames can be of sheets of glass and a variety of patented
moved around the garden and placed on metal clips, they were cumbersome and
ordinary beds in different positions as re- breakable but very efficient. Rigid plastic
quired. Traditional forms have permanent sheeting has largely taken over from glass for
bases of brick or w o o d . this type of sectional cloche. The most recent
development is the tunnel cloche made of
Frames can be built along the sides of half- , strips of flexible plastic sheeting stretched
boarded greenhouses in order to benefit from over a series of wire hoops along a row and
surplus warmth from the greenhouse. held in place with further hoops over the top.
The ends are anchored firmly by burying
The simplest form of frame is just a light, them in the soil. Ventilation is by pushing up
a glass or plastic panel, placed over a shallow the plastic on the side away from the wind.
pit. This allows pot or container plants to be
hardened off.

Structure materials 1

The superstructure of a greenhouse may be Unlike the wood-frame greenhouses once Metal is a good conductor of heat and cold Wood
made of wood, aluminum alloy or steel. Pre- widely sold, aluminum structures do not need and for this reason, condensation drip can be However wood greenhouses are still popular
stressed concrete, used for larger houses, is painting. This lack of regular maintenance is a nuisance in metal-framed houses. This heat for aesthetic reasons. The attractive colors of
too thick and heavy for smaller structures. a big factor in their popularity. conduction factor also means that metal redwood, cedar and cypress fit much better
houses are colder, or cool more rapidly than into the garden than the color of bright
Metal Steel is also used in greenhouse construc- timber-framed ones, though the differences aluminum or steel.
Most custom-built greenhouses are made of tion, either totally, as in some large commer- in temperatures between the two are small.
wood or aluminum alloy. The latter is now cial houses, or in conjunction with an alloy in Unless the regular maintenance of painting Providing a wood house is properly con-
by far the most popular material, being light smaller ones. The steel must of course be gal- and putty renewal is considered a pleasure, structed and secured to a brick or concrete
and strong and easily extruded into the vanized or treated in other ways to prevent aluminum or steel and aluminum houses are base and is initially treated with a wood pre-
necessary shapes ready for bolting together rusting. Although generally adequate, after much to be preferred to the various wood servative (if the wood is not naturally decay-
on the site. At one time, corrosion was a time the galvanizing treatment breaks down houses, even those made of decay-resistant resistant), there is every chance it will out-
problem, especially in areas of industrial air and rusting becomes a problem. Galvanizing redwood, red cedar or cypress, or other live its owner. Further painting with a wood
pollution and near the sea. Modern alloy is can also be broken down by an electrolytic woods that have been treated with wood preservative, or better still, linseed oil about
much more resistant so that corrosion is only reaction when alloy and steel members preservative. A metal greenhouse will allow every five years or so is a wise precaution.
likely to occur in areas of very high industrial touch. This factor is now well known however the gardener to spend more time in the Apart from the aesthetic considerations,
pollution, which are not widespread. and seldom occurs in well-designed smaller greenhouse than working on it. wood has some advantages when it comes to
amateur greenhouses. installing extra shelving, securing wires for

Aluminum frame greenhouses are light to penetrate. The model shown has Cedar requires little maintenance and aluminum houses, but they have the
maintenance-free and have narrow glazing diagonal bracing struts for stability, a sliding blends well into the garden surroundings. advantage of being easily drilled for
bars, allowing the maximum amount of door and cement plinth foundations. The glazing bars are thicker than in fixings and plant supports.

Structure materials 2

i climbers ,andl hooks for hanging baskets. frame on a low wall of brick or concrete. If PAINTING AND PRESERVING W O O D followed by two gloss coats for maximum
Metal houses arcesometimes drilled for these this is not possible then redwood or metal protection. Softwood greenhouses are
purposes but so often these holes seem to alloy should be chosen. The surface must first be prepared before without question more difficult and costly
lx> where they are not needed and drilling it is treated. Brush down to remove dirt to maintain than the more expensive
extra ones is not easy without the right equip- Cloches and grit then wash the surface and allow hardwood greenhouses. The life of the
ment. Extra holes also often penetrate the to dry. Rub the wood down with a medium greenhouse may be doubled if the wood
protective coatings on alloy and steel, leading Class and plasticform the bulk of a cloche and glasspaper or wet-abrasive, which is easier is treated with a preservative which is
to corrosion. are discussed on pages 10-11. Glass cloches and prevents dust from flying about. When toxic to decay organisms. Preservatives
are secured by various patented methods repainting it may be necessary to strip should be applied to the greenhouse by
Frames using stout galvanized wire or steel alloy back and reprime if the paint is blistered the manufacturer before the greenhouse
The same considerations and comments re- brackets in conjunction with wood or plastic or cracked as moisture is rapidly absorbed is constructed. They usually consist of
garding aluminum or steel and timber in the buffers. The latter method makes assembly once the skin of the paint is broken. copper or mercurial-zinc compounds,
construction of greenhouses applies also to and dismantling easy but it must be used with either in a water-soluble form or in a
frames. Since a frame is generally used in care when the cloche is constructed of Softwood greenhouses will need paint- spirit solvent.
conjunction with a greenhouse it should be larger sheets of glass. Rigid plastic cloches are ing every other year. Use an aluminum
of the same materials. If wood is selected secured either by galvanized wire or are primer if any bare wood is to be seen after Guttering
do not sit it directly on the soil. M o u n t the molded to shape and free-standing. Tunnel which an undercoat should be applied
cloches require U-shaped wires or canes.
Tubular steel frame Doors

Steel tube frames are used for film-clad and consequent repeated maintenance Sliding and hinged doors are available. Some aluminum greenhouses have built-in
greenhouses. Among the cheapest frame work is to be avoided. Do not allow contact If possible, ensure that the base of the guttering, with others it is an extra. It avoids
materials, steel must be galvanized if rust between steel and alloy components. doorway is flat, or provide a ramp. drips and aids water saving.

Covering materials 1

Glass is the traditional glazing material for a stretched tightly over the superstructure. the type of fiberglass made specifically for Sunlight and the greenhouse
greenhouse, and for a long time was the only Loosely secured material can act like a sail greenhouses should be used; the familiar Heat builds up rapidly in a greenhouse when
material suitable for the job. Although plastic and, because of the movement, chafe against porch-roof material should not be used. the sun is shining and can easily reach limits
sheeting has become more popular, glass is its supports during strong winds. These lethal to plants without ventilation and/or
still the most widely used material. Most of the factors can spell disaster before the natural Perhaps the greatest advantage of fiber- shading. Light and heat from the sun reach
glass used for greenhouses is single-strength life of the sheeting is reached. glass is its exceptionally high resistance to the earth as short-wave radiation, which
sheet glass. However, double-strength is breakage—a compelling reason for using it passes easily through glass and plastics. This
preferable. From a light transmission point of One advantage of polyethylene is that it is in a neighborhood of rowdy children or radiation warms everything it touches, such
view, the larger the pane size the better. so light that the greenhouse can be built frequent hailstorms. This factor, coupled with as the floor, benches, soil, pots and even the
There are also fewer heat-leaking joints with without foundations (although it must, of its good resistance to ultra-violet, means it plants themselves, which then re-radiate
large panes, although they are more expen- course, be anchored to keep it from being should last between 10 and 15 years. Make some of this heat as long waves. It is because
sive to replace if any get broken. blown over). Hence it can be moved around sure that it is not exposed to flame or ex- glass does not allow these long waves to pass
the garden if desired. tremes of heat, because it burns readily and through it that a build-up of heat inside the
Glazing rapidly. greenhouse results. Once shadows reach the
The technique of securing the glass to the A disadvantage of polyethylene is that it greenhouse, or after the sun sets, heat is
superstructure is known as glazing. In the radiates heat rapidly. Because of this it is Because fiberglass is translucent, the light lost via air flow through cracks and as long-
past glass was installed in overlapping sheets often applied in a double layer and a small admitted to the greenhouse is soft and wave radiation via solid walls and the basic
like shingles. The side edges were slipped into fan used to blow air between the sheets in shadowless. This feature makes the panels framework.
grooves in the mullions or were puttied, but order to reduce heat loss. especially attractive in the West, where light
there was no sealant along the top and Vinyl Vinyl sheet is heavier than poly- intensity is high. Radiation is diffused as it enters a poly-
bottom edges, thus allowing a fairly free ex- ethylene, more durable and considerably Acrylic Semi-rigid, usually flat acrylic panels ethylene sheeting greenhouse and the sub-
change of inside and outside air. Today, the more costly. If made with an ultra-violet in- are ideal for greenhouses because of their sequent long-wave radiation is not trapped.
glass is used in larger pieces and is fixed into hibitor, it can last as long as five years. But it strength, light weight, resistance to sunlight For this reason, polyethylene sheeting-clad
the framing members by various methods. comes in narrow sheets that must be heat- and good light-transmission characteristics. structures, including frames and cloches,
In some cases putty or an equivalent material seamed, which greatly adds to the difficulty They do scratch easily, but apart from this cool down more rapidly than glass ones once
is used. Class allows about 90 per cent of the of installation. Also, like polyethylene, it has their principal disadvantage is their very high the sun has gone, though the differences are
sun's radiation to pass through but filters out electrostatic properties that attract dust, cost. However, acrylic is worth the outlay not really significant in most climates. Once
the ultra-violet part of the spectrum. Ultra- which clouds the sheeting and therefore as it will give good service for many years.
violet light is not, however, essential to plant cuts down the transmission of light. Traditional putty glazing (a). Dry methods
growth and in excess it can be harmful. Polyester The best known of the polyester Glass should be free of flaws and bubbles, (b, c) are used with metal-framed houses.
films is Mylar. In the 5-mm thickness used for which act as lenses and scorch plants.
Where the sun's heat is excessive and can greenhouses, it has the advantages of being
lead to scorching of plants, translucent glass lightweight, it is strong enough to resist
can be used; but this will cut down winter damage by hail, it is unaffected by extreme
light penetration considerably. In temperate temperatures and has light-transmission
climates some form of shading is a preferable characteristics quite similar to glass. Mylar is,
alternative in hot weather. however, expensive.

Plastics Mylar should last about four years on
Plastic sheets and panels perform the same sturdy framed greenhouse roofs and longer
functions as glass in greenhouse coverings on the sidewalls. It will not be so effective
and have the advantage of being cheaper and when used on poorly built frames that are
non-breakable. rocked by wind.
Polyethylene Polyethylene is applied in huge
sheets that make for faster glazing, but it Fiberglass .Plastic panels reinforced with
has a short life span. Normally it needs to be fiberglass are considerably heavier than film
replaced after one growing season. Poly- and much more durable. They retain heat
ethylene with ultra-violet inhibitors lasts better than other glazing materials but are
about twice as long. Although the material also more expensive.
does not break like glass, it is weakened by
ultra-violet light and often splits during gales; The panels are semi-rigid and come in long
indeed on windy sites even new sheeting may lengths up to 4 ft in width. The most common
split. It is important that the sheeting be weight of fiberglass used by amateurs is 4 or
5 oz, although heavier weights are available.
The panels are either flat or corrugated. The
latter are generally used only on greenhouse
roofs because of their greater strength. Only

Covering materials 2

the greenhouse heats up, convection cur- large, steeply inclined panes are the most The position of the sun varies widely from rising and setting of the sun is 60°, in
rents arise and the warm air moves in a cyclic effective. winter to summer and this variation must summer 120°. In winter only the south-
fashion, varying somewhat with the shape be considered when planning the location facing side of this greenhouse receives
and size of the house and the amount of During the winter, sunlight in northern and choosing the type of greenhouse. In direct sun, in summer the ends too face
ventilation. In theory, convection currents regions reaches the earth at a low angle. winter, the arc between the points of the sun at morning and evening.
warm the whole area, in fact there are often Therefore greenhouses with walls set at a
small pockets of cooler and warmer air. slight angle present a surface at right angles,
or almost so, to the sun's rays, allowing
Light maximum penetration. In summer the angle
Good glass allows about 90 per cent of total is not so crucial as the intensity of the sun-
illumination to enter the greenhouse. This light is far greater.
includes reflected light from all sources.
Direct sunlight must strike the glass at a The position of the sun varies during the
90 degree angle for the maximum amount day, moving through an arc that varies from
of light to enter. If the angle of the sun varies about 60 degrees during the winter months
from this angle some of the light will be de- to 120 degrees or more in the height of the
flected. During the summer months there is summer. Thus a flat surface receives light at
more than enough light for most plants, but the optimum angle for only a short time. The
during winter it is in short supply. For this round greenhouse solves this problem by
reason a fair amount of research has gone presenting glass surfaces at different angles
into finding the best greenhouse shapes for so that the plants receive light of sufficient
good all-year-round light transmission. As a intensity throughout the year. Some green-
result round greenhouses have proved to be houses have been designed to rotate so that
the best shape for this purpose. The angle at surfaces are exposed to the sun as required.
which the glass is set is obviously important
and among traditional greenhouse designs, Round greenhouses, however, are still not
as yet readily available. Most greenhouses,
Sun angles and the "greenhouse effect" whether bought ready-made or built, are of
the lean-to variety or tent-shaped.

Noon, Summer. The short rays from the sun the glass. Thus the temperature rises. A Noon, Winter. In winter, the angle of the to reflect some light, which is lost. Sloped
pass through the glass (a) and heat soil, plastic-clad house (b) does not get so hot glass surfaces to the sun becomes sides (b) allow light to pass t h r o u g h at right
benches and walls. Heat is reflected as because reflected long waves can pass important as the sun angle is lower and the angles and light transmission through the
long rays, which cannot pass out through through plastic, which also diffuses light. light intensity less. Vertical sides (a) tend glass is improved.

Site and situation 1

All too often, the greenhouse is relegated to entrance, as is usual for sun-rooms or the Shelter Although a solid wall or a close-boarded
a distant corner of the garden or to a site larger type of lean-to or conservatory. This For the free-standing greenhouse it is impor- fence may seem the ideal, the turbulence
which is far from ideal for the plants to be arrangement makes it possible to use the tant to choose a protected site or at least one factor must be taken into consideration, par-
grown. If a greenhouse is being purchased same heating system to heat both house and with some shelter from the coldest prevailing ticularly in areas frequently subjected to
and particularly if the expense of heating it is greenhouse, with a saving on installation and wind. The stronger and colder the wind blow- gales. W h e n wind strikes a solid object such
contemplated, then the best situation pos- subsequent running costs. If the lean-to is ing across the glass, the greater the heat loss. as a wall, it swirls over the top and causes
sible must be found. Failure to choose the built against a south, south-east or south- Some estimates make the loss caused by turbulence on the other side, the distance
best position could mean the disappointment west-facing wall, winter light will be good and wind as high as 50 per cent when a cold away from the wall that the turbulence ex-
of poor quality flowers, fruits and vegetables. shelter assured. winter gale is blowing. Some gardens, of tends depending on wind speed. A hedge or
In many cases, space in the garden will be course, are well sheltered by buildings and open-weave fence diffuses the wind and
restricted and there will be only one possible A greenhouse will get much more use, and vegetation. Wind problems in such gardens breaks its main force and in this respect is
site. Even so, this site can be adapted to give the plants in it will get more care, if it is easy will be restricted to eddies and occasional to be preferred. Such a barrier is effective
the best possible conditions. of access. Other considerations such as severe storms. over a downwind distance equal to five to ten
aspect and shade may take precedence, but times its height, so even if a barrier has to be
Choosing a site other things being equal it is best to site the Trees, even if they do not cast shadows placed to the west or south-west of the green-
Basic considerations are good light and greenhouse as close to the home as possible. over the greenhouse, can cause problems by house to counter prevailing winds, it can be
shelter from strong winds. Good light is Wherever it is placed, make sure that there rain drip onto glass, and can shed branches sited far enough away to avoid shade
especially important if plants are to be grown are hard-surfaced paths leading to it. This will which can badly damage the greenhouse. problems.
during the winter months, and without some allow the use of a barrow to transport heavy The roots of nearby trees can also damage
sort of wind shelter heat losses will be con- items such as compost and plants. foundations and intrude into planting beds. Foundation and erection
siderably greater than they need be, especi- Creating shelter If it is not possible to find a Once the position of the greenhouse has
ally during cold spells. If the site is chosen in If possible the greenhouse should be close sheltered site, a hedge can be planted, or a been decided upon, the terrain must be
summer, and there are tall buildings or trees to frames, if they are used, and the seedbed. fence erected to provide a windbreak. If this examined carefully. Ideally the ground should
to the south, the shadows they will cast in Often greenhouse plants will be moved to or is positioned at a distance of at least three be level and well drained. If the site slopes or
winter must be calculated. In the latitude of from the frame, and many seedlings will be times the height of the greenhouse on the is very uneven it must be at least roughly
New York City the sun at noon on the shortest planted out into a frame or seedbed for north, north-east or north-west side, shading leveled. When leveling the site, take care to
day is poised about 28° above the horizon growing on. Frames can be placed against will be virtually nil.
and all shadows are long. Winter sun angles the walls of a half-boarded greenhouse. 3 The upper arm will now point to the
can be reproduced with the aid of a pair of 2 Place the lower arm of the sighting angle lowest midday sun position. By sighting
calipers and a compass. A simple substitute Measuring shade areas with a sighting angle on a spirit level at the planned position of along this arm it is possible to estimate
for the calipers is two straight flat pieces of the greenhouse. Point the sighting angle which trees and buildings will cast shadows
board about 1ft long, joined at one end by a 1 To check if a site is likely to be shaded, south, making sure that it is exactly level. over the planned site of the greenhouse.
single nail or screw. Open the calipers thus find out the lowest angle of the winter sun.
formed at the required angle and, keeping Join two pieces of wood with a screw. Using
the lower arm horizontal, point the upper a protractor, carefully set the pieces at the
arm due south. If the part of the sky where required angle. Tighten the screw.
the arm points is widely obscured by trees or
buildings, then shade is likely to be a problem.

To take full advantage of the light from the
low winter sun, the greenhouse should be
positioned with its long axis aligned east-west
or as near to this ideal as possible. This posi-
tion cuts shading from roof beams and astra-
gals (glazing bars) to a minimum. An east-west
position also allows the rays of the sun to
penetrate at the most efficient angle (see
page 11).

Access There is no doubt that, to get the
most enjoyment out of a greenhouse, especi-
ally in winter, easy access from the house is
essential. The ideal is to have the greenhouse
physically attached to the house with a direct

Site and situation 2

remove and conserve the top-soil especially have been uncultivated or under grass for cement to harden before the superstructure Water supply
if a glass-to-ground greenhouse with soil beds several years. For greenhouses of 10 x 8 ft or is built or glazed. The period required varies Even if it is decided to use rain water butts as
is planned. Do not compact the soil when larger however a proper concrete foundation with the weather and the proportions of the a water source, these can run dry in dry spells
leveling the site and erecting the greenhouse. is necessary. concrete mixture used. Allow at least 48 and there is much to be said for a per-
Undue pressure can destroy the soil struc- Marking out the site Whether of compacted hours, more in cool weather. If glazing takes manent water supply in the greenhouse. If an
ture, leading to drainage problems and loss of soil or concrete, it is most important that the place after the structure goes up this should automatic or semi-automatic watering system
fertility. finished surface is level. The site should be be carried out during dry, calm weather. The or a mist propagation unit is planned, run-
accurately marked out using the plans sup- same applies to the erection of sections pur- ning water is essential. W i t h modern plastic
If the site is wet, some sort of drainage plied with the greenhouse. Carefully check chased already glazed. If glazing is carried out piping and fittings the installation of a supply
system should be installed. A row of tile drains that the base or foundations are on the cor- over a period of days there is much to be said is not difficult, though a professional plumber
down the centre of the site with a sump or rect alignment, using part of a building or a for doing the roof first. This allows the wind, must be called in to make the connection
drywell at one end is usually enough, or a boundary line as a fixed point. Having estab- should it arise, to pass through the structure. to the main supply. The supply pipe is best
concrete platform can be made with its sur- lished a straight line along one wall of the A half-glazed house with a strong wind blow- laid at the same time as the foundations. If it
face just above the surrounding soil. If the greenhouse, carefully measure a right angle ing on to the inside can be badly damaged. has to be added later, take care not to
greenhouse is to be erected on a sloping site, for the end wall (see below right). A spirit level Class can be very slippery when wet and damage the foundations.
ensure that there is drainage to cope with is an essential tool during preparation. If the ideally should be handled only in dry weather.
water running down the slope from above. base or foundation is not level, erection of In addition, the putty and mastic seals used Electricity
Construct a gutter to channel water around the superstructure may be difficult, or it will in traditional glazing do not stick satisfactorily Even if a greenhouse is not heated by it, a
the greenhouse if necessary. sustain stresses and strains that later could in wet conditions. If guttering is to be fitted supply of electricity gives many advantages.
Bases and foundations All custom-built green- lead to trouble. Most small greenhouses are to the greenhouse some thought should be It is necessary for heated propagators, mist
houses are sold with detailed erection instruc- erected level, though some are provided with given to rain water disposal at this stage. Rain units, soil-warming cables and artificial illumi-
tions. Many models have an integral or a slight fall to allow gutters to function. water butts provide a useful water reserve if nation. Lighting is a very worthwhile extra,
optional base, made of shaped sections of certain precautions are taken (see page 25). for its installation allows the greenhouse to be
concrete which are laid on the soil. No other Particular attention should be paid to the Alternatively, a drywell must be dug nearby used on winter evenings, adding a novel
foundation is needed for the smaller green- anchoring method, especially in windy sites. and piping laid to it or to a nearby drainage dimension to gardening under glass. For
houses providing the site is firm and If sill bolts have to be cemented in place, ditch or watercourse. details of electricity, see page 17.
accurately leveled. Ideally the soil should make sure enough time elapses for the

Walls, hedges and fences must be sited to winds yet casting no shadow. The fence to Mark the position of one side of the green- square, to establish the position of one
block, or preferably filter, wind, yet not cast the north can be sited closer to the house, using two pegs and a taut line. end wall. Repeat to fix the remaining
shadows over the greenhouse. The 6 ft greenhouse, as it will not cast a shadow. Check that the pegs are level. Then care- corners. Check that all eight pegs are level.
hedge above is south and west of the Use hedges or openwork fences as shelter fully measure a right angle, using a T A spirit level is an essential tool.
greenhouse, cutting the force of prevailing belts where possible as they filter the wind.

Ventilation and shading 1

Owing to the "greenhouse effect" (see p. 11), as optional extras so it is possible to rectify when cold winds are blowing. This practice eliminate it. Before installing louvered venti-
which causes a rapid build-up of heat inside the deficiency. cuts down damaging cold drafts. All venti- lators, check that they are reasonably draft-
the greenhouse when the sun shines on it, an lators must be easily adjustable from closed free when closed.
efficient ventilation system is essential to When warmed, it is the nature of air to to wide open. This is particularly important
control temperature. Ventilation is also become less dense and to rise. For this reason for the ridge ventilators which, when fully Ventilator mechanisms
necessary in order to provide a supply of ridge vents are all-important for releasing open, should ideally continue the line of the In the small greenhouse ventilators are oper-
fresh air and to control humidity. Stale air over-heated air. As the hot air rises up and opposite side of the roof. This is equivalent ated by hand, being opened and secured by
provides ideal conditions for the spread of passes out of the ventilators, fresh cool air is to being openable to about 55 degrees. Less the same perforated bar and pin method
diseases and pests. Ventilation must be con- sucked in through the glass overlaps, glazing than this will mean that maximum ventilation used for some factory windows. In larger
sidered a factor in the maintenance of a cracks, and around the doors. For full and is not possible. However, there are practical greenhouses, particularly those with venti-
balanced greenhouse environment. It must adequate ventilation the overall area of the difficulties to such an installation and many lators too high to reach, a variety of open-
be matched to heating, shading and the ridge ventilators should be equal to at least small houses have ventilators which open ing methods are used, including cranks and
control of humidity. one-sixth of the floor area, more if feasible. less wide. A fully open ventilator at this angle gearwheels, pulleys and cords, and rack and
For the smaller greenhouse alternate ventila- is also an efficient wind trap, directing a cool- pinion.
Despite the advances made in small green- tors either side of the ridge or at least two per ing current downwards into the greenhouse.
house design few models, if any, are provided 6 ft length are usually adequate. For larger This air-flow warms and rises up to exit via Automatic ventilators All the manual meth-
with enough ventilators to cope with warm structures or those used as alpine houses the the lee side ventilators, thus ensuring a rapid ods, however efficient in themselves, rely
summer day temperatures without opening provision of continuous ventilators along air exchange on sunny days. entirely on an efficient operator. Forget-
the door. While using the door as an emer- both sides is ideal. fulness can result in loss of or damage to
gency ventilator is acceptable for some crops Air movement through side and ridge valuable plants. This factor, added to the
and on quiet days, it should never be con- Air exchange and subsequent cooling is ventilators can be strong on windy days and frequent absence of the gardener during the
sidered standard practice. For manufacturers, faster if side ventilators are also fitted. These create drafts unwelcome to many tropical day, has given the impetus for the invention
more ventilators means design modification can be just above ground or at bench level. foliage plants and orchids. To cut down the of automatic mechanisms. Initially, and still
and extra material with the inevitable in- Ventilators should be installed in both posi- force of this airflow louvered ventilators have widely used in the better-equipped nurseries
creased costs. However, most greenhouse tions if possible. Ventilators should be posi- been designed. However, while they can cut of commerce and public gardens, came the
manufacturers can supply more ventilators tioned on both sides of the greenhouse so down the full force of a draft they cannot electric motor coupled with lifting gears and
that those on the lee side can be opened
Air flow Side ventilators

Ventilators in both roof and sides allow Ideally, roof ventilators should open to Side or wall ventilators speed air exchange closed. Louver ventilators are useful when
complete air circulation within the about 55°, thus continuing the line of the and cooling. They can be conventional orchids or other tropical plants are being
greenhouse. Roof vents can also act as roof when fully open. Ventilators should be (above) or louver (above right). Check that grown as they cut down, but do not
wind scoops in hot weather. positioned on both sides of the roof. louver installations are draft-free when eliminate, drafts.

Ventilation and shading 2

controlled by a thermostat-activated switch, Ventilator fans almost flush with the wall of the greenhouse. Plan fan installations carefully, taking
more recently and now popular for the While the methods of controlling ventilation In place of glass are a series of louvers or flaps account of the capacity of the installation to
smaller greenhouse, a system has been per- described above work adequately, particu- which hang down and cover the gap when make the necessary air changes. The placing
fected which is triggered by a heat-sensitive larly in the small greenhouse, the natural air the fan is not working. Under air pressure of inlet openings is important with fan venti-
compound. The compound is contained in a currents upon which they rely are not totally from the working fan, the louvers assume a lation. Site the inlets to allow cross-drafts to
strong metal cylinder, one end of which is efficient in maintaining a perfectly uniform horizontal position. The same system, but in occur, thus stimulating air movement. Damp-
closed by a plunger, the other end being climate. In larger structures in particular, reverse, can be used for the inlets at the other ing pads can be placed over inlet openings to
blanked off. On heating, the compound ex- there may be unsuspected pockets of warm end or the side opposite the fans, thus pre- moisten incoming air in hot, dry conditions.
pands, pushing the plunger forwards. This or cool air which can locally affect plant venting unwanted ventilation when the fans About 40 air changes an hour is the right rate
comparatively small amount of pressure is growth. To eliminate this factor and to cut are not working. The fans are usually operated to aim for.
magnified by a system of levers which open down drafts and conserve heat, ventilator automatically, being coupled to a pre-set
the ventilator. Closing is gradual once the fans are used. The usual high speed fans used thermostat. Humidity
compound starts to cool. Most types can be in kitchens and bathrooms are unsuitable, Humidistats, which work on the same prin-
adjusted to open at various temperatures. as they can create artificial drafts, and low In general, the smaller the fan the higher it ciples as thermostats but respond to humidity
The more sophisticated systems control ven- speed fans, which can move large volumes of should be set in the greenhouse wall. In the rather than temperature, are used in com-
tilators according to a full range of weather air, have been designed. Ventilator fans are small amateur greenhouse, one fan installed mercial greenhouses. They have the effect of
conditions. Wind gauges actuate motors to also useful in plastic-clad greenhouses, where above the door is a usual recommendation, avoiding any excess build-ups of humidity by
shut ventilators to avoid drafts. A rain water vapor condensing on the plastic may while the big 4ft fans used in commercial turning on fans for short periods and thus
gauge can be linked to ventilator controls to raise humidity unduly. A fan will prevent this houses are set at various heights, depending circulating the air. One effect of fans, especi-
shut down the house in the case of rain, by circulating fresh air. upon the crop. The use of fans within the ally in smaller greenhouses, is to dry the air.
though simple temperature controls, which Installing fans Ventilator fans should be in- greenhouse, to circulate air rather than to If a fan is used as the main means of ventila-
will respond to increased cloud cover and stalled at one end of smaller houses or at ventilate, is usually coupled with heating, but tion, some form of damping down or other
the resulting temperature drop, produce the intervals along one side of larger structures, when the artificial heat is not in use it is humidity control should be practised in warm
same effect. Sunlight-operated controls are with ventilators at the opposite end or side. beneficial to leave the fan on to maintain a weather. Automatic spray systems can be
another refinement. Each fan is set with the blades parallel to and buoyant atmosphere which is vital for the obtained for this purpose.
healthy growth of many greenhouse plants.

Fans

Ventilators can be opened by hand (top), when heated. This expansion operates a Position a ventilator fan above the door of A louvered ventilator must be positioned at
automatically (above) or by remote control plunger, which pushes the ventilator open a small greenhouse. Use only slow-running the opposite end of the greenhouse to a fan
(right). Automatic systems consist of a via a system of levers. Remote systems fans designed for greenhouses. to provide a flow of air.
cylinder of a compound which expands are used in large houses.

Ventilation and shading 3

Shading is a greenhouse necessity that is Methods of shading warmth just when they need it most. For this Blinds Slatted blinds of wood or plastic laths
easily overlooked. While in winter every effort Shading can be carried out in two basic ways, reason the use of blinds is more efficient and are best, being long lasting and rolling and
is made to maximize the amount of sun re- by painting or spraying liquid onto the glass, to be preferred. Roller blinds can be fitted unrolling easily. A certain amount of light
ceived, in spring and summer too much sun- or by blinds. Lime wash was once a standard either to the outside or inside of the green- penetrates the blinds, but individual plants
light can quickly overheat the greenhouse, liquid shading and well-diluted emulsion house, and Venetian blinds fitted to the are not harmed as the angle of the sun
killing plants. Some form of shading system is paint has also been used. If applied too interior. Exterior blinds are the most effective changes slowly during the day. Also good arc-
therefore essential. It must, however, be used thickly, both of these substances tend to stick as they prevent heat build-up. Blinds on the blinds made from white suffused plastic
in conjunction with ventilation and watering on tight and need hard rubbing to remove at inside of the glass stop light reaching the sheeting, and Venetian blinds. Ideally, and
with the aim of maintaining a balanced the end of the season. Proprietary com- plants but the heat penetrates the glass and especially for the greenhouse owner away
greenhouse environment. All too often pounds are now available which rub off easily, warms the greenhouse in the normal way. each day, the roller blinds should be auto-
shading is used simply to reduce heat and the yet are not affected by rain. All the traditional Although they can be neat and easily used, mated, the unrolling mechanism coupled to
maintenance chore of watering. shading substances are likely to be thinned internal blinds can also be a nuisance where an electronic eye or thermostat. This of
or washed off during heavy rain and will need lots of tall plants with leaves or flowers near course adds greatly to the cost. Where auto-
In greenhouses where ventilation is efficient replacing if hot weather continues. All liquid the glass are grown. In general, blinds fitted mation is not contemplated, the owner of the
there is much to be said for not shading unless shading should be white. Green paint—and to the outside of the house are to be pre- smaller greenhouse can easily devise make-
absolutely necessary. Sun-loving plants in green blinds—absorb heat, while white ferred, though weather hazards must be shift shading for a few hot spells. Window-
particular, such as succulents, will grow more reflects it. taken into consideration, particularly that of like frames of strong laths or canes can be
sturdily in full light. Where a very varied col- strong wind. Exterior blinds can be rolled covered with opaque plastic sheeting or light
lection of plants is grown it is not difficult to The primary disadvantage of liquid shading down in winter to provide a certain amount burlap and hung or clipped to the green-
position them so that the shade lovers are is that, during summer's inevitable dull, cool of protection against frost. house sides and roof, inside or out.
behind those that need or tolerate full light. spells, plants suffer from lack of light and
Automatic shading Improvised shading
Methods of shading

1 Shading paint is applied 2 Exterior blinds prevent 3 Interior blinds are less Exterior blinds can be unrolled and Improvised screens can be made f r o m
to the outside of the glass heat build-up and cut down effective than exterior ones, retracted by motors triggered by light- burlap or cloth, and cloth or plastic sheet
in spring. Do not apply too light. They can also be but are neat and easily sensitive devices. This is expensive, but can be pinned or stuck to the outside
thickly. useful as frost protection. used. useful on greenhouses often left unattended. of greenhouses.

Electricity 1

Although it is possible to run ,1 greenhouse greenhouse control panel. Choose only those Cables laid underground should be A control panel simplifies the installation of
without an electricity supply, lack ol power installations designed for greenhouse con- protected against accidental damage while electricity in the greenhouse. All equipment
|)uts many of the techniques of modern ditions. A control panel allows several pieces digging. Cover the cable with a treated can be controlled from the panel, which has
horticulture out of the gardener's reach. A of equipment to be run from one point. plank or place tiles over it. fused, switched sockets.
whole range of appliances from heaters to Fused, switched sockets are provided with an
pest control equipment depends upon a independent main switch. The main power Thermostats should be set to the Fan heaters can be used to back up other
power source. Electric light also makes it cable has only to be connected, the sockets temperature required in the propagating heating systems or as a system on their
possible to use the greenhouse for more being ready wired. The equipment is then case or soil cable unit. Check the own. Use only those designed for
hours per day in winter. plugged in in the normal way. Always use manufacturer's literature for the greenhouses, which can withstand damp.
fused plugs, if possible made of rubber temperature range the appliance controls.
Installing electricity rather than plastic.
House electricity out of doors is a matter for a
professional. Amateur gardeners are not Lighting
recommended to attempt installation, for the Strip or bulb lighting, using heavy-duty damp-
risks are great. Cables will have to be laid proof fittings, is relatively easy and cheap to
outdoors unless the greenhouse is a lean-to install once a power supply is available. Light-
adjoining the home, and the environment of ing will increase the use a greenhouse gets
the greenhouse itself raises dangers due to during winter, making it possible for the
high humidity and damp. gardener who is away during the day to
attend to the plants in comfort.
If cables have to be installed, plan the
route they are to take with the aid of an elec- Lighting installations can also be used to
trician. Cables can be buried or suspended speed plant growth and to modify growth
from posts. Buried cables should be sunk rates to produce special effects. Many plants
in trenches at least 2\1/2 deep. Route the are very sensitive to "day length", the period
trenches where they will cause least disturb- during which light is strong enough for growth
ance to garden plants, lawns and trees. When to occur. During winter in northern areas, and
burying the cables, the electrician will pro- in areas with high atmospheric pollution, this
tect them from accidental damage by cover- level is often not reached. Banks of strip
ing them with a board or a row of tiles. lights are used commercially to modify the
Such a protective layer will prevent damage day length and bring plants into flower out-
when digging or carrying out other cultiva- side their normal season. Install lights about
tions in the garden. Make sure that trenches 3 ft above the greenhouse bench, in banks
do not interfere with drainage systems. sufficiently large to provide the light intensity
Cables buried beneath paths or lawns need required. Consult specialist suppliers of green-
not be so deep, but wherever they run, a house equipment for details of light levels
record should be kept of their position so and periods. Too much light, or too long a
that if the layout of the garden is changed "day", is often worse than too little, as many
the gardener is aware of the exact position plants have very specific requirements. Use
of the cables. mercury vapor lamps, as the type of light they
produce is best for plant growth. Banks of
Cables taken overhead must be fixed to a fluorescent tubes can also be used, mounted
stout wire supported on poles well above the 2 ft above the bench.
ground. Keep the cable clear of trees which
may chafe it. The gardener may be able to Other electric equipment
save on the electrician's bill by doing un- Propagating equipment, watering devices
skilled preparatory work such as digging and ventilation equipment are described on
trenches or erecting poles. Consult the elec- the appropriate pages. Equipment used in the
trician and agree on exactly what is to be greenhouse must be made for the purpose.
done by whom before starting work. Do not, for instance, use domestic cooling
fans and fan heaters as they may be affected
Power points by the damp atmosphere in the greenhouse
Inside the greenhouse, the power cable and become dangerous.
should terminate at a purpose-designed

Heating 1

In the cooler temperate regions where frost Thus if the likely minimum temperature of the
occurs regularly in winter, sun heat alone is area is — 2°C, and a cool greenhouse is plan-
too weak and unreliable for the successful ned the temperature must be raised by 6°C
growth of tender plants under glass. There- and the heating system must be adequate.
fore to get the best out of a greenhouse an
artificial heat source must be installed if only Greenhouses have higher heat losses than
to keep the minimum temperature above the other, more solid, structures and are more
frost limit. An alternative is to use a heated prone to drafts. Also, heat is lost quickly
propagating case as a "greenhouse within a through glass so cold spots can easily develop
greenhouse" to allow seeds and cuttings to be if the heating system is not carefully designed.
started earlier than in the greenhouse itself. A single stove or radiator placed in the center
It is possible to run a greenhouse without any of the greenhouse will not necessarily warm
heat—see the Cold Greenhouse section the whole air space, which is the reason why
(page 64)—but a heat source which, com- pipe systems are popular. To check for cold
bined with insulation, maintains the temper- areas, place several maximum-minimum
ature above freezing, is almost essential. thermometers at intervals around the green-
house and leave them overnight. Alter-
The first question to ask when planning a natively, use a single thermometer, placing it
heating system is what level of heat is needed. at different points on nights with the same or
Two factors must be taken into account. They very similar air temperature.
are the prevailing weather conditions in the
locality and the needs of the plants to be Before calculating heat needs, check what
grown. There are certain levels of tempera- can be done to improve the insulation of the
ture which must be maintained if various greenhouse. Double glazing is the most
types of plants are to be grown (see Intro- effective means of cutting heat loss. Per-
duction, page 2). Refer to the map, right, manent double glazing is heavy, costly and
for the lowest likely temperature. Consider can interfere with light transmission, but is
the modifying effects of height, exposure and becoming a more attractive option as better
proximity to the coast, which can raise or systems are designed and fuel costs continue
lower minimum temperatures. to climb. Alternatives to permanent double
glazing are temporary plastic sheet double
Once the minimum temperature needed glazing or the use of insulating panels on the
in the greenhouse has been decided, the lower parts of the greenhouse sides.
temperature increase required can be calcu-
lated. This is the number of degrees that the Drafts should be stopped wherever pos-
temperature must be raised above the likely sible, not only because they increase heat
minimum to be encountered in the locality. loss but because drafts can interfere with the
working of heating systems.

CALCULATING HEAT LOSS a heating system capable of raising the The map above divides North America of growing season. When calculating
temperature by 4,000 BTU's- is needed. into ten zones of hardiness. This zone greenhouse heating needs, use the map
Use the map right to establish the tem- Heaters and fuels have their heat outputs system was devised by the Arnold Arbor- to assess the local minimum temperature.
perature rise required. Then calculate the quoted in BTU's/hour so the size of heating etum at Harvard, and is widely used by The difference between the expected mini-
rate of heat loss. First measure the glass installation needed can be calculated. scientists and gardeners. The zones are mum and the temperature desired in the
area of the greenhouse in square feet. Each Bear in mind additional heat loss from defined in terms of consistent average greenhouse is the necessary temperature
square foot of glass will lose 1.13 British wind, through gaps in the structure and annual minimum temperature and length increase the heating system must provide.
Thermal Units (BTU's) of heat per hour for through necessary ventilation. Measures
each degree F of temperature difference taken to reduce heat loss such as double
between inside and out. Thus if there is glazing reduce the amount of heat needed.
360 sq ft of glass and the temperature Heat loss varies with material: the all-glass
difference between inside and out is 10°F, figure quoted gives a slight over-estimate
the heat loss is 4,068 BTU/hour (360 x 10 for a part wood or brick house.
x 1.13). Thus in order to maintain a tem-
perature 10°F above the likely minimum,

Heating 2 Supplying oxygen to heaters

Air circulation

Wind can lower the temperature of the Allow a gap between benches and stagings Leave a ventilator open while combustion Alternatively, install a door or wall vent
exposed side of the greenhouse. Adequate and the sides of the greenhouse to permit heaters are in use. Avoid drafts over which will provide enough oxygen for
air circulation helps to avoid cold spots. air to circulate. plants. combustion without creating drafts.

Checking for cold spots Insulation

Check for cold spots in the greenhouse by greenhouse or, if only one is available, vary Insulation can be applied in the form of using tacks or a staple gun. Remove
using one or more maximum-minimum its position noting minimum temperatures special panels (left) or plastic sheeting, right, insulation as soon as the weather moderates
thermometers. Place them around the on nights of similar outside temperature. which should be fixed in double layers for it will impede light transmission.

Heating 3

Solid fuel piped hot water systems time. Large installations may have a main burning correctly, dangerous carbon mon- Natural gas heating
Heating water by burning solid fuel is a cheap constant-level system of the water tank and oxide fumes will be given off instead of carbon Natural gas burnt directly in special heaters
method of heating a greenhouse. Modern ball-valve type. dioxide and water vapor which is beneficial to is very efficient. Its by-products carbon
furnaces burning coal, anthracite, and other plants. Ensure that the flue fitted to the fur- dioxide and water vapor which enhance the
special fuels are designed to reduce stoking Oil-fired piped hot water systems nace is tall enough to carry fumes away from greenhouse atmosphere make the com-
and the clearing of ash to a minimum. Many Solid fuel furnaces may be adapted to burn oil the greenhouse. Regular maintenance should mercial greenhouse practice of atmosphere
have quite good thermostatic control but or a purpose-built system can be installed. be carried out on all furnace systems to avoid enrichment, which encourages the plants to
are not so accurate as the more easily con- Oil-fired systems can be thermostatically problems with fumes and fuel wastage. grow, available to the amateur gardener. As
trolled fuels such as electricity and gas. Water controlled: an efficient thermostatic control the burner is sited inside the greenhouse,
heated in a boiler within the furnace circu- system reduces the amount of attention Linking greenhouse and domestic systems regular maintenance is necessary in order to
lates through a system of pipes. The pipes, required to maintain a constant temperature. Where a lean-to greenhouse or sun room avoid possible emission of poisonous gases
which must rise gently from the boiler, should Large, specially manufactured oil-fired in- is to be heated and a hot water radiator such as carbon monoxide. The natural gas
be of narrow-diameter aluminum rather than stallations are highly efficient and automatic. system is used in the home, it is sometimes systems on the market are thermostatically
the large-diameter cast iron type. Furnaces possible to link the two. However, it is controlled and fully automatic, with a safety
are rated in terms of heat output as BTU's/ Gas-fired piped hot water systems advisable to consult a heating engineer first, valve which prevents the main supply from
hour. Choose a furnace large enough to heat Gas furnaces are easy to operate and may be and best if possible to incorporate the green- being turned on unless the pilot flame is
the greenhouse to the desired temperature fully automatic, being controlled thermo- house heater in the home system when it is alight. It is more convenient to use a piped
(see page 18). Only the fuels recommended statically. Care should be taken to site the installed rather than to add later. Problems natural gas supply in c o n j u n c t i o n with a
by the maker must be used. The pipes are furnace where its fumes will not be carried can arise with a linked system because special greenhouse heater which is portable
best filled with soft water such as rainwater, into the greenhouse. Gas fumes can be greenhouses need heating at night, whereas to some extent. Bottled natural gas such as
and will have to be topped up from time to dangerous to plants. If the furnace is not homes are heated during the day and evening. propane or butane tends to be expensive

Piped systems circulate hot water from a lower pipe to the furnace. This kind of The small-bore piped system uses narrow pipes and a circulating pump may be
furnace through pipes laid around the system, using large-diameter cast iron pipes, aluminum piping. Because of the extra needed. A header tank (illustrated) tops up
greenhouse. The hot water rises from the is less efficient than the small-bore system, friction in smaller pipes, the water does not the water in the system. Such furnaces
boiler, slowly cools, and returns via the right, which has mostly superseded it. rise by convection as freely as in large can be fuelled by solid fuel, gas or oil.

Heating 4

although it is convenient where piped produce water vapor as they burn which Siting a boiler downwind, so that the prevailing wind
supply is not available. Propane is advisable keeps the greenhouse atmosphere moist, carries smoke and fumes away.
when the storage bottle is kept outside as although ventilation is necessary at times as Fumes from a furnace can harm plants. Site
butane does not readily volatilize in cold the atmosphere may become excessively it therefore outside the greenhouse and
weather. The larger the bottles or cylinders, humid. When combustion is taking place the
the more economical is this type of heating. greenhouse must be ventilated to provide an
oxygen supply. Keep the heaters clean and
Kerosene heaters the wick trimmed according to the maker's
Kerosene is the simplest form of heating to instructions. Features to look for when buying
install. Choose a heater that is designed for a kerosene heater are stainless steel lamp
the greenhouse, as some household kerosene chimneys, fuel level indicators and large,
heaters give off fumes deadly to plants. separate fuel tanks to make filling easier and
Greenhouse heaters are specially designed to less frequent.
reduce the risk of fumes and are often
equipped with tubes or other devices to Electric heating systems
distribute the heat evenly around the green- Electric heating is the most efficient and
house. They are, however, difficult to control effective. It is easy to control, clean and is the
thermostatically. A flue is a desirable feature, safest for use with plants as there are no
since some models may tend to produce fumes. It must be fitted by an electrician as
harmful fumes. Some have hot water pipes the combination of electricity and damp can
as well as hot air ducts. Kerosene heaters be lethal (see page 17).

Where pipes run across a doorway, lay Electric tubular heaters distribute warmth Natural gas heaters heat the air by the Kerosene heaters must be carefully
metal grilles above them to allow heat to evenly in the same way as piped hot water burning of a gas which is harmless to plants maintained to avoid harmful fumes.
rise yet protect the pipes from damage. systems. They can be mounted in banks or if the burners are correctly adjusted. Piped Choose a model with a large, easily-filled
installed singly in greenhouse cold spots. or bottled gas can be used. fuel tank and a fuel level indicator.

Heating 5

There are many different types of electrical Soil heating cables 1 Remove the border soil to a depth of 2 Lay soil heating cables on the soil
heating apparatus especially developed for There are many advantages to the gardener 9 in. Pile the border soil to one side and surface. Space the cable in a series of loops
greenhouses. Tubular heaters have a similar in warming the soil from below. Crops may be rake over the base of the trench produced. 4—6 in apart. Do not let the loops t o u c h .
capacity for even distribution as hot water raised earlier than normal and cuttings and Peg the cable down with staples.
piping systems. Position along a side wall of seed germination should be more successful. 3 Replace the border soil and rake it level.
the greenhouse in a single line or group Water the bed lightly. Damp soil conducts 4 Connect the soil heating cable to a
together at points around the greenhouse to There are two good methods of warming heat better than dry. thermostat, if one is supplied with the cable
give more heat to colder areas. the soil using cables. The first utilizes bare kit, or direct to an outlet. Carefully follow
cables buried 6-9 in below the surface of the the maker's instructions on installation.
There are compact fan-assisted heaters soil with low voltage current passed through
which are easily moved and will spread the them by means of a transformer to step down
heat over the whole area of the greenhouse. the primary voltage. Alternatively, insulated
They may also be used to circulate cool air soil-heating cables are used in conjunction
when heat is not needed. Thermostatically with the full house current buried 6-9 in
controlled fan heaters will accurately control below the surface.
temperatures to within one or two degrees
with no waste of fuel or heat and need little The soil is excavated to the required depth
maintenance. Fan heaters circulate air, keep- and a layer of sand spread over the bottom
ing the atmosphere buoyant and reducing of the trench and raked level. The required
the chance of fungal disease. The best type of length of cable, as recommended by the
fan heater has separate thermostats con- manufacturer, is laid over the surface in
trolling the fan and the heat, supplying heat parallel lines as evenly spaced as possible.
when it is needed. When the fan is switched The cable is then pegged in position using
off the air will remain relatively motionless galvanized wire pegs.
except for convection currents. The advant-
age of this system is that there will be inter- There is no need for special precautions to
mittent air circulation with little heat loss. protect the wire when using a low voltage.
However, 115 and 230-volt cables can be
The fan-heated greenhouse can be safely dangerous if accidentally severed. It is there-
left closed during cold weather as there is no
contamination of the air and no need for HEATING COSTS
extra ventilation.
At a time when the relative prices of the
Convection heaters are another type of various fuels are fluctuating, it is impossible
efficient electric heater. They consist of a to give a realistic indication of what it
cabinet with holes at the top and bottom costs to heat a greenhouse. Two key
with heating wires inside which warm the air. points emerge from any study of heating
The warm air rises and flows out at the top costs. First, waste of heat, through inade-
causing cold air to be drawn in at the bottom. quate insulation, drafts and poor ad-
In this way convection currents cycle the air justment of heating systems, is a major
around the greenhouse. factor in most fuel bills. Second, the effect
of raising the greenhouse temperature
Storage heaters can be economical using from cool to warm level is to double bills.
the off-peak rate for greenhouse heating.
This type of heating is, however, difficult to Therefore the decision to grow warm
control thermostatically. There will some- greenhouse plants is one that must be
times be too little and sometimes too much taken with an eye on the cost. Also,
heat. They are best used for background careful management and heat conserva-
warmth in conjunction with a main heat tion can make all the difference to the
source keeping the maximum temperature economics of greenhouse heating. The
thermostatically. An accurately controlled flexibility of the various fuels must be
electric heater can be used to maintain the considered as well as cost. Electricity,
maximum temperature level with a kerosene especially when used to power fan heaters,
heater for background warmth. The advan- is very flexible and little energy is wasted
tage of using a combination of heaters is that providing unwanted heat.
the more expensive fuels are conserved.

Heating 6

lore a good plan to lay ,1 length ot galvanized accurate thermostatic control is possible SOLAR HEATING Heat storage
mesh over the cable. Spread sand over the with electric heaters, and for this reason
mesh and then replace the soil. Plug the other types of heater use electricity to All sources of heat are solar in the sense Warm air is sucked by a fan down a duct
cable into a waterproof outlet which is operate motors or electro-magnets which that their fuels are derived, however from the roof space, where sun heat is
placed well above the level of the soil where regulate the flow of fuel. A thermostat usually distantly, from the power of the sun. Oil, greatest during the day. Rocks below the
there is no danger of it getting wet. has a graduated dial which is set to the coal, and gas, and electricity generated floor store heat. At night, the fan reverses.
required temperature which the thermostat from them, are fossil fuels produced by Solar furnace
Soil-heating cable kits are available com- will then maintain, if the heating system is nature from sun power. Because these
plete with thermostats, although the ther- powerful enough. fuels are expensive, increasingly scarce
mostat is not essential. Soil-heating installa- and liable to interruptions in supply,
tions vary in power. They usually provide a Conserving heat in the greenhouse many attempts have been made to har-
temperature of 16°C/60°F. Heat will be lost through broken and cracked ness the sun directly. Two linked problems
glass, ill-fitting doors and vents, which must immediately arise: timing and heat stor-
Thermostats be repaired or improved. age. The sun tends to shine when heating
The various heating systems described may is least required, so some means of heat
all be controlled by special greenhouse Lining the greenhouse in winter with storage is essential. None of the systems
thermostats. A thermostat is a device that polyethylene sheet to give a "double glazing" available can be said to overcome these
controls the temperature of the atmosphere effect will help enormously (see page 22). Use problems so completely that they can be
in the greenhouse by regulating the fuel the thinnest and clearest polyethylene sheet recommended as a sole system of heating.
supply to the heater. Two strips made of available. It is the static air trapped between
different metals, joined together within the the plastic and the glass that forms the insula- Solar heating has two uses at the present
thermostat, expand and contract in response tion—so do not leave gaps. So that vents can stage of development: as a back-up heat
to changes in temperature. The movement be opened, line them separately. source and as an area for experiment by
of this bi-metallic strip switches electrical technically-minded gardeners. The illus-
contacts which control the flow of fuel, or the Burlap or old blankets placed over the trations on this page show the principles
flow of air to solid fuel, thus regulating the roof at night in extremely cold weather will behind some of the solar heat methods
speed at which the fuel is burnt. Very conserve heat. They must, however, be in use.
removed in the morning.
Warm-air duct heating Water panels and heat storage

Polyethylene ducts, which may be greenhouse eves. First used in commercial Water is pumped up and flows over roof The sun heats air behind the glass wall,
perforated, distribute heat given out by an greenhouses, they are an efficient means of panels. The sun heats the panels and the causing it to rise. W a r m air flows into the
electric fan heater or a gas heater fitted distributing heat in larger greenhouses. water, which is stored in an insulated tank. heat storage of rocks, which are heated. At
with a fan. Such pipes can be installed At night, flaps are opened to let heat out. night warm air is pumped from the storage.
either below benches or along the

Water supply and watering 1

Every greenhouse should have a piped supply can be installed over the tank to replenish for watering plants on shelves and lor Automatic watering: Pipe systems these
of water, unless it is very small or is close to it when rain fails. If water reserves of these measuring out liquid fertilizer, fungicides and methods of watering involve piping and
the house or an outside faucet. Despite the kinds are contemplated, it must be borne in insecticides. A gallon can is the most useful. finer tubing or nozzles. Trickle systems are the
contrary preferences of some gardeners, mind that mosquitoes and other pests will It should feel balanced and comfortable to the most popular. In its simplest form this is
city water is perfectly acceptable for plants, breed in static water. Water from tanks can grasp. It should have a tapered extension piping perforated at intervals and so arranged
and, unlike rainwater, the piped supply is also act as a distributor of fungal and bacterial spout for plants at the back of benches and that a perforation is over each pot, or by
unlikely to fail. However, guttering is useful plant diseases. on shelves, and a fine rose for watering newly- each plant to be watered. Somewhat more
in itself in preventing drips from the green- sown seeds or pricked-off seedlings, or for sophisticated versions have nozzles or a
house and it is sensible to store the water the If running water is installed in the green- damping down floors. If high-level shelving length of tubing from each perforation. In the
gutters channel. Rainwater storage requires house, make sure the water piping is well or hanging baskets are fitted, obtain a so-called spaghetti system a sheaf of very
careful planning and attention to hygiene if buried to prevent freezing. Install the pipes, smaller 1/2 or 3/4 gal can with a long, curved small-bore tubes runs from the end of a
water butts are not to become havens for which can be of modern plastics with com- spout. Cans are made of galvanized or hose. Each tube is then led to a pot and
waterborne pests and diseases. pression fittings, when the greenhouse is enameled metal or plastic, the latter being clipped into place. These methods can be
being built. Fit a faucet chosen to suit the now the most readily available. Plastic is set to trickle indefinitely, or the water supply
If stored rainwater is to be the only source watering equipment likely to be used. A cheaper than metal and lighter to handle. can be set to a solenoid valve and linked to a
of supply, at least two 60 gal butts will be range of modern hose couplings and connec- Automatic watering: Capillary benches time clock to run at set intervals.
needed for a fully-stocked 8 x 8ft green- tions for automatic watering devices is Watering plants properly by hand can be a
house, and even then the reserves will be available, allowing several watering systems time-consuming job, requiring knowledge If a slow non-stop trickle is used the pots
used up during a dry spell. Butts should have to be used at the same time. and experience. There are several methods of must be inspected regularly. Large, vigorous
tight-fitting lids to keep out leaves and other watering plants automatically, whether in plants may need more water than the trickle
debris which can foul the water. Two or Watering systems pots or beds. Where a large collection of pot can deliver, and will suffer as a result.
more butts can be connected by overflow Once a supply of water is assured, watering plants is maintained and especially if the Overhead sprinklers can also be used on an
pipes to store surplus water. An alternative to systems can be chosen. These range from owner has to be away during the day, a automatic basis and for plants w h i c h need
butts is a tank within the greenhouse or simple cans to automatic devices. capillary bed system is a worthwhile invest- a high humidity they are ideal. Care must be
even under the floor, with pipes leading from Cans Even if automatic watering devices are ment. This method works on the capillarity taken, however, to see that all plants are
the guttering. With this arrangement, a faucet favored, a watering can will still be necessary of moist sand. That is, water is sucked up getting an adequate water supply. The dense
through the tiny spaces between the grains or broad foliage of some potted plants can
WATERING CANS shelves and hanging baskets to be easily of sand through the drainage holes into the effectively prevent enough water from reach-
reached. A fine rose will be required for pot. Line a deep bench top with heavy gauge ing the rootball beneath.
Watering cans should be durable and watering seeds and delicate seedlings and plastic sheeting, and fill with washed sand
well-balanced. A long, possibly sectional, rooted cuttings. to a depth of 2-3 in. Special trays can also While all these self-watering methods are
spout is useful in a crowded greenhouse be used. The sand is kept continually moist invaluable to the greenhouse gardener, they
and a small can allows plants on high on the surface but not waterlogged, either must be used intelligently. As with all forms
with a watering can or an automatic device. of automation, they are non-selective and
The simplest of these is the inverted demi- this is a disadvantage where living organisms
john or header bottle in a shallow reservoir, are concerned. Every plant will get the same
which overflows directly onto the sand amount of water whether it needs it or not.
or into connecting guttering. A more fully Some will respond by growing lush and out of
automatic system uses a header tank con- character, others may become waterlogged
nected to a piped water supply and fed to and slowly die. Where a wide variety of plants
the sand bench via a ballcock valve. The pot is grown, they must be inspected regularly.
plants, which should not be crocked, are Over-wet plants must be taken out of the
pushed into the top inch of the sand with a automatic system for a while to dry out,
screwing motion so that sand is forced into while dry ones must be given extra water
the drainage hole or holes and makes by hand.
contact with the soil. Water is taken up into
the soil by capillary action. Humidity
Although water is primarily used for keeping
An alternative to sand is the so-called the roots moist, most plants appreciate or
capillary matting which is kept wet in the need humidity in the air, at least when in full
same way. It can however, become clogged growth. This too can be provided by automa-
with algae after a time and then needs tion, using overhead or near-ground nozzles
careful washing or replacing. such as those used in mist propagation
systems (see page 30).

Water supply and watering 2

Storage butts Internal tanks Connecting fittings Header tanks

Water butts should have tight-fitting lids. Guttering can be led into the greenhouse Special fittings replace faucets and allow Header tanks and bottles supply water to
Two or more can be connected by pipes. to fill an internal water tank. Fit a tight- several appliances, such as hoses and a capillary and trickle irrigation systems by
Faucets allow cans to be filled. fitting cover to keep insect pests out. header tank, to be used at once. gravity.

Capillary bench Capillary matting

The capillary bench watering system plants take up water from the sand through An alternative to a sand bench, capillary Water can be supplied manually or by a
consists of a polyethylene-lined tray filled the pots' drainage holes. Push the pots matting soaks up water which is then header tank or bottle. The matting becomes
with sand. The sand is moistened and the into the sand with a screwing motion. taken up by plants by capillary action. clogged with algae after a time.

Water supply and watering 3

Watering allowed almost to dry out (or dryish potting Spray lines Trickle irrigation
All watering under glass requires care, espe- mixture can be used at the outset). Each pot
cially that of plants in containers. In the is then weighed in the hand, watered tho- Fine sprays of water directed by nozzles Trickle systems supply a small a m o u n t of
beginner's greenhouse at least, more plants roughly and checked again. A method onto plants are an efficient way of both water continuously to each plant. Check
are likely to suffer or die from lack of, or too formerly much used involves the use of a watering and raising humidity. plants regularly.
much, water than succumb to pests and tapper, easily made from a length of cane Trickle irrigation—spaghetti
diseases. Watering is a skilled operation, not and a small block of w o o d about the size of coupling, deliver water to each plant. A
even all professional gardeners fully master it. a cotton reel. Each pot is rapped smartly in The so-called spaghetti system works on the header tank can be used to give a
Like so many other aspects of gardening turn and if a ringing tone is given out the root same principle as the trickle system. continuous supply, or a timeswitch fitted.
under glass, it is essential to get to know the ball is dry and watering is needed. A dull, Flexible tubes, attached to a central
plants well. In time, personal observation hollow noise denotes that the rootball is
will provide the experience that is required to moist. This only works with clay pots.
judge accurately the needs of each plant at
any time of the year. The above methods can be used success-
fully on healthy actively growing plants. They
Watering containers are less easily applied to dormant or resting
Water plants in containers by filling the space plants which require keeping barely moist.
between the soil surface and the pot rim with Provided a free-draining potting medium is
water, thus ensuring that the whole of the used, ideally a loam-based mixture, applying
root system is moistened. Frequency of just half the usual amount of water at each
watering depends on several factors, notably application is usually successful. All-peat pot-
the vigor of the plant, temperature, type of ting mixes shrink away from the sides of the
soil, and the container. A fast growing, well pot when kept too dry and much of the
rooted plant will probably need watering subsequent water applied runs down the
each day in summer, perhaps even twice sides. To overcome this difficulty the plants
daily during a hot spell. In winter the same should be stood in trays of water so that the
plant may need watering only once or twice a bottom half of each pot is submerged. Unless
week, or even less if it has a definite resting the soil is dust-dry, a few minutes in water
period. will suffice to moisten it adequately.

If in doubt as to when a plant needs water, Watering beds
there are several useful observations that can Beds and borders in the greenhouse are
be made and points to check. Wilting or watered in much the same way as those in
flagging of the plant is very obvious when in the outdoor garden and it is even more
an advanced state but the observant gar- important to use a rose or sprinkler on the
dener will note the slight drooping of soft can or hose. This prevents panning of the
stem and leaf tips which precedes this, soil surface and unsightly soil-splash on
denoting a need for water. Whatever the lower leaves of small plants. As with pots,
soil mixture used it is always paler in tone beds must be attended to regularly and
when dry. When this state is reached in a thoroughly. It is all too easy to think the bed
clay pot, watering is required. In a plastic pot has been well watered when in effect it is
however, this indication is not so reliable, as still dry several inches down. Many a crop
containers of this sort are not porous and the of grapes, peaches or tomatoes has been
soil stays more moist below the surface layer. spoilt for this reason. The equivalent of at
If the plant is not growing vigorously or the least one inch of rain should be applied each
weather is cool, it is advisable to scratch into time. To get a rough idea of this amount,
the surface of the soil with the finger tip. stand a straight-sided container on the bed
If the top 1/4 in of the soil is dry, then water- during watering. When an inch is measurable
ing should be carried out. An estimate of in the bottom, leave for at least an hour then
the weight of a pot full of soil can also dig a small hole about 6 in deep and if dryish
be used as a guide. To enable the weight soil shows at the bottom of the hole, water
differences to be recognized, a range of pots again.
should be filled and firmed as for potting and

Benches and staging 1

Kent lies and staging of some sort arc used in maintain plants at bench level—most heat, cold and sunlight, and that plants Uses for solid benches A solid top to the
most greenhouses, the only exceptions being benches and stagings are 2 1/2 ft high. The placed on them will need extra care. Finally, bench or staging allows beds of soil, sand or
those houses used entirely for growing crops plants are also nearer eye level, allowing ensure that there is easy access to all plants. gravel to be formed. These can range from
in the border soil, those devoted to tall con- them to be better appreciated. Benches and staging should be no more than thin layers of gravel on which containers are
tainer plants and possibly those lean-tos 4 ft deep, and shelves, pot holders and hang- stood, to aid drainage and increase humidity,
which are primarily used for growing fruit Other kinds of structure such as shelves, ing baskets should be placed where they do to 4 - 6 in deep beds of sand or soil. Such beds
against the rear wall. Benches are less per- pot holders, orchid baskets, and hanging not impede normal work in the greenhouse. are essential if mist propagation or the use of
manent than stagings, a term used to refer baskets for ferns and trailing plants can also Keep hanging baskets, for instance, above soil heating cables are to be practiced.
to robust long-term constructions often be fitted into the greenhouse. Take care not normal head height unless they are sus- Gravel trays are watered in summer with the
supporting raised soil beds. to over-crowd the greenhouse, for too many pended over a bench or other area away aim of increasing humidity. Solid-topped
structures will cut out light, impede air circu- from the central path. Shelves can be placed benches are also needed if trickle irrigation
The use of benches and staging has several lation, and allow high-level plant containers across the end of the greenhouse, opposite systems are contemplated. Hydroponics sys-
advantages. They multiply the amount of to drip onto those below. the door, it they do not obstruct side benches. tems, which rely on a flow of nutrients in
useful growing space available, as the area liquid form, need solid benches. Shallow
underneath them can often be used. This is Positioning benches Types of bench and staging metal trays can be used to convert per-
especially true in glass-to-ground houses, The first choice to be made is between solid forated benches into solid ones.
where enough light will penetrate the area Take account of the aspect of the greenhouse and perforated tops. Both have their advan- Materials The choice is between metal
beneath the benches to grow crops such as when planning the position of benches and tages, and the choice depends to a large frames, wood frames and permanent brick
lettuce and to raise seedlings in boxes and staging. If the axis of the house is east-west, extent upon the crops to be grown and the or concrete stagings. Metal and wood frames
pans. In half-glazed houses the area beneath then one bench on the north side is ideal, as type of cultivation to be carried out. Air can be fitted with perforated or solid tops.
the staging can be used for forcing crops such it does not block light. The south soil bed can circulation around benches is not so critical Some benches are removable, giving flexi-
as rhubarb and seakale and for storing dor- be used for crops, and adequate light will in summer, when more ventilators will be bility in the arrangement of the greenhouse.
mant plants during winter. Plants grown on reach plants on the bench. Place high-level open. Then, perforated benches may be Wood will need to be thoroughly cleaned at
benches are likely to receive more light than shelves where they will not cast shadows over covered with plastic sheet or metal trays to least once a year as it can harbor pest and
those placed on the floor or grown in soil other plants for an appreciable portion of the allow solid-bench techniques to be used. disease organisms.
beds. It is also easier to water and generally day. Bear in mind that shelves raised near to
the roof glass will be subject to extremes of
Types of staging

Staging can be timber or metal-framed, or and in summer can be covered with plastic maximum air circulation allowing heat to releasing at night heat absorbed during the
supported on brick or concrete piers. sheet which can be spread with moisture- circulate. Metal trays can be laid on the day. Concrete is also strong, and can
Slatted w o o d staging (a) is traditional and retaining vemiculite, gravel or peat. Net- staging and filled with gravel (c). Solid similarly support raised soil beds and heavy
attractive. It allows air circulation in winter, topped stagings (b), with metal frames, give brick staging (d) acts as a heat reservoir, pots, but it retains less heat t h a n brick.

Benches and staging 2 Displaying plants

Shelves

1 Metal or wood shelves can be fixed to 2 Tiered staging displays large numbers of Pot holders allow plants, especially trailers, Hanging baskets can be suspended from
glazing bars on the sides and roof of the pot plants attractively. It is available in to be mounted on the greenhouse sides. brackets mounted on walls or from the
greenhouse. Use special clips on aluminum wood or metal and can be placed on the They can be bought or improvised from greenhouse roof. Use those fitted with drip
frames. Make shelves at least 6 in deep. ground or on staging. bent wire. trays if they are placed above other plants

Displaying orchids Shelves under staging Hardening-off shelves

1 Many orchids grow best in perforated 2 Epiphytic orchids can be grown on thick Shelves can be mounted under staging in Some greenhouses are equipped with
containers or wooden baskets, which can pieces of bark. Wrap roots in compost and glass-to-ground houses, especially on the opening panes allowing flats of plants on
be suspended from the greenhouse roof. wire the plant and rootball to the bark, south side. Use shelves for pots of bulbs shelves below the staging to be slid into the
(See pages 84-85) which is hung from the roof. during their dormant periods. open by day and returned at night.

Benches and staging 3

Solid brick and concrete stagings can he from the roof beam if there is enough head- WIRING A WALL
built as part of the structure of half-glazed room. Proprietary fastening systems have
greenhouses with a brick base, lhey are very brackets which can be adjusted to the dis- Rear walls of lean-to greenhouses can be wall and make maintenance and repair
strong, and also have the advantage of in- tances between the greenhouse frame bars. used to grow fruits and ornamental to the framework difficult.
creasing the amount of heat the greenhouse Shelves should be wide enough to take the plants. Careful preparation pays dividends
can store and release during the night. Sun pots envisaged, strong, and easy of access. later on, when the plant will cover the First scrub down the wall with water and
shining through the glass strikes the staging Bear in mind the need to water the plants. a dilute horticultural disinfectant to kill
and heat is stored in the same manner as in Tiered shelves Banks of tiered wood or metal
a brick or stone wall. This heat is given off shelves can be installed in place of normal pest and disease organisms. If the wall is Fix 2 in square w o o d battens vertically
during the night, moderating the temperature benches, or can be mounted upon the bench of brick, repoint and render if possible. at either end of the wall. Using straining
drop in the greenhouse. Brick is a much more itself. They are of most use where large num- Then whitewash or paint the wall to bolts at one end, stretch wires horizontally
efficient storer of heat than concrete, and bers of ornamental pot plants are grown, provide a light-reflecting surface. between the posts, 15-18 in apart.
therefore brick structures should be chosen allowing the largest possible number of
if heat storage is an important factor. Choose plants to be displayed.
hard-faced bricks which are less porous than
the normal sort. These are easier to scrub Hanging baskets
down and less likely to harbor pest and Hanging containers may be essential if many
disease organisms. trailing ornamentals are grown, and in any
case such containers are attractive. Baskets
Bench-top beds are made of metal, or preferably plastic-
covered metal. They are filled with soil mix
Soil beds at bench level are described on and lined with moss (see page 54). Place them
page 46. They need strong brick or concrete carefully where drips will not be a problem,
staging and by their nature are permanent. and ensure that fastenings are strong enough
Less permanent beds can be formed by add- to support the combined weights of con-
ing raised edges to solid-based benches. Such tainer, plants and wet soil.
benches can be covered with soil, sand or
gravel. The use of soil heating cables re- Pots can be suspended in wire or cord
quires a bed of sand or soil 4 in deep, in which "cradles", or in the decorative purpose-made
the cables are buried. Power cables of special holders designed primarily for house plants.
type are used to raise the sand temperature Drill plastic pots to take the wire; clay pots
to 43°C/110°F, and the sand transmits the can be fitted into a sling.
heat to pots and flats of plants and seeds Pot holders Simple metal rings attached to
placed upon it. Soil-heating systems are fre- brackets can be used to support pots. Fix the
quently used with mist propagation. rings to greenhouse frame uprights.

Alpine houses frequently have stagings Permanent supports
topped with a tray containing 4-6 in of Plant support systems are discussed on page
gravel, into which the pots containing the 50. Permanent supports, such as the system
plants are plunged. Again, a strong per- of wires illustrated right, must be planned
manent structure is essential. Alpines can when other fittings such as benches, staging
also be grown in bench-top beds. Often t w o and shelves are being considered. In a lean-
beds are constructed: one filled with stony, to house the rear wall can be wired for the
acid soil, the other with a free-draining growing of espalier or cordon fruit trees or
alkaline soil. climbers. Walls should be scrubbed down,
preferably with a fungicide, rendered if
Shelves necessary and then painted or whitewashed
The use of narrow shelves above the main before the wires are fitted. Trellising can be
bench or staging maximizes growing space fitted to battens and hinged at the bottom to
and allows pot plants to be placed where they allow the wall behind to be painted. This is
are attractive yet not in the way of propaga- only necessary for very long-lived plants such
tion and other bench-top activities. Shelves as vines. Full details can be found in Gardening
may be fixed to the glazing bars or suspended Techniques in this series.
from them. Shelves can also be suspended

Propagating aids 1

All gardeners like to propagate their own humidity, temperature, gas content and light propagated successfully without protection able cost, they are much to be preferred to
plants, at least by the two basic means of transmission; and the environment of the For these reasons a properly-constructed inexpertly-made or put together do-it-your-
sowing seeds and taking cuttings. The prin- medium (soil or compost), which covers tem- self frames. The cheaper custom-built cases
ciples and methods of propagation are dealt perature, moisture, aeration and chemical heated propagating frame or case is highly have cable heating which maintains a tem-
with on pages 55-63, the equipment used, on reaction (acidity/alkalinity). The job of propa- desirable. In addition, the larger propagating perature around 65"F/18"C. If outside con-
the next two pages. gation equipment is to modify these factors cases can be used to house a small collection ditions are cold, however, the temperature
to provide the optimum conditions. of tropical plants in a cold or cool greenhouse. can drop much lower and for this reason ,a
Most tender plant seeds germinate more The ideal environment An ideal environ- more efficient heating unit coupled with a
readily if kept at a temperature a little warmer ment is one that allows minimum water loss Propagating cases thermostat is desirable. If tropical plants are
than is required by the growing plant. Seeds from the plant, cool air temperatures, Basically, the propagating frame or case is a being propagated, it must be possible to
of hardy and half-hardy vegetables and adequate light penetration, a normal atmo- smaller version of a garden frame. It provides maintain a minimum temperature of about
flowers are often sown under glass in late spheric balance between soil and air, good a closed high-humidity environment and can 75°F/24°C. Sophisticated units have both
winter or early spring before the weather is drainage and warm soil temperatures. The be used either in the greenhouse or indoors if bottom heat to warm the soil and cables
warm enough outside. The main problem in acidity/alkalinity reaction should be neutral. light is adequate. The case can be of wood or around the sides to warm the air.
propagation is to ensure survival of the The degree to which a particular system of aluminum, with a cover of glass or plastic Unheated propagators If most of the propa-
propagated material (be it seed, cutting or environmental control operates will limit the sheeting. Bottom heat can be supplied elec- gation is done from late spring to late sum-
graft) until it forms a new young plant. If the propagation techniques that can be used trically by soil heating cables (see page 22) mer, bottom heat is not so important and a
correct material has been used at the start, successfully within it. In general, the "softer" or custom-made units with built-in heating wide variety of custom-made propagators
and properly prepared, then success is or less hardy the plant material the greater elements can be purchased. Small units are without heat are available. Like the heated
directly related to the control of the environ- will be the degree of environmental control heated by light-bulbs fitted to the end walls, ones, they are largely of plastic, the bottom
ment by the gardener. needed to achieve success. The vagaries of or by fluorescent lighting tubes. For the being like a seed flat, the top an angular
the normal outdoor climate are too great amateur there is now a wide range of easily- dome of clear rigid plastic. Home-made
Environmental factors In plant propagation for all but the easiest and hardiest plants to be portable propagating cases with a heating frames of wood and glass or plastic sheeting
there are two environments: the aerial en- unit as an integral part. Generally of reason-
vironment, which can be broken down into

A mist unit provides fine sprays of water in trols the soil heat, and a cut-off switch, An ordinary seed flat, pan or pot can be Purpose-made propagators have a domed
the air above the plants, which are thus responsive to light, moisture or time, the converted into a propagator if polyethylene plastic top over an ordinary seed flat.
constantly covered by a fine film of water. water supply. Sunlight is uninterrupted as sheeting is spread over hoops and sealed. Ventilators are usually fitted.
Such a unit is used in conjunction with there is no need for a glass or plastic cover.
soil-heating cables. A thermostat con- Mist units can cover entire benches.

Propagating aids 2

CAN be just as effective and for small-scale way. As a result, a high level of photosynthesis will raise the temperature excessively , in Heated propagators
propagation some of the rigid plastic boxes tan continue from the moment of insertion closed cases, sometimes to lethal limits.
sold for food storage are useful. Simplest of and subsequent rooting is more rapid and Shading must then be provided for all propa- Small propagating cases are heated by a
all is a plastic bag with either the pot of assured. There can be weaning problems gators enclosed with glass or plastic. This can light-bulb in a glass-covered case. Flats are
cuttings or seeds placed inside, or with the with some of the more difficult to root plants be done by shading the cases or frames placed on the glass.
bag inverted over the pot. If the latter method once they reach the potting stage. themselves or the glass of the greenhouse
is used, two U-shaped loops of galvanized above. Any of the shading methods described
wire can be pushed into the rooting medium The system known as intermittent mist on page 16 can be employed, though the
to prevent the bag from collapsing onto the is also useful. The spray nozzles are coupled permanent or semi-permanent liquid prep-
cuttings or seedlings. to a solenoid positioned among the cut- arations are less desirable in climates where
tings. When the solenoid dries sufficiently it long, dull spells can be experienced at any
Mist units actuates a switch to start the misting again. time of the year. Ideally, shading should be
For the gardener who is particularly keen to Another method is triggered by an absorbent used only on bright days or during sunny
propagate plants of all kinds, a mist unit will pad attached to a switch. When the pad is spells so that photosynthesis is not curtailed
ensure a higher rate of rooting success and wet and heavy it presses down and turns the more than necessary. A position at the north
give much interest and satisfaction. Mist system off. W h e n dry it rises and turns it on side or end of a greenhouse is best.
propagation requires electricity and piped again. Where the growing season is persist-
water supplies. It keeps the foliage of the ently warm and sunny, misting nozzles may The mist propagation method requires
plant material moist with a fine mist-like be left on, or just shut off at night. little or no shade in temperate zones, parti-
spray of water, thus eliminating the need for cularly if the unit is sited at the north side or
light-reducing covers of plastic or glass. The Siting a propagator end of the greenhouse. In areas of hotter
sun's light and heat can fall onto the cuttings Whatever propagation equipment is chosen summer sun, light shading during the middle
with only the greenhouse roof glass in the it must be sited with care in the greenhouse. part of the day may be necessary unless con-
Adequate light is essential but direct sunlight tinuous misting nozzles are used.
Soil heating
Thermostat Roof shape

Soil-heating cables or heated panels in the An adjustable thermostat allows the internal A sloped roof causes condensation to run A kerosene-heated propagator can be used
base heat the growing medium in larger temperature to be maintained at the to the sides of the roof, avoiding harmful where there is no electricity.
propagators. required level despite weather changes. drips onto plants.

Introduction/Hygiene 1

Of all the branches of horticulture, growing Summer A routine for an imaginary summer Winter Much the same procedure is followed Hygiene
under glass is the most specialized. Not only day could be as follows. Once the morning in winter, but if the weather is cold and tem- Along with the right environment and routine
is the constant maintenance of the plants sun is fully on the greenhouse, check the peratures do not rise, ventilation and damp- care, a good level of hygiene must be main-
necessary, but the environment must be con- temperature. If it is about five degrees above ing will not need to be carried out and water- tained to ensure healthy, vigorous plants
trolled to give acceptable growing conditions. the desired minimum temperature for the ing will be minimal. The need to keep the greenhouse and parti
The ideal environment The basic aim should plants being grown, open the ventilators by cularly the glass clean is often overlooked. II
always be to create an ideal environment for half to two-thirds. If temperatures continue While this sort of routine is ideal for the is surprising how much dirt can settle firmly
healthy growth, but perfection is seldom to climb, open up fully around mid-morning. plants, it is not easily carried out by the onto a sheet of glass in the open, even in
possible, and never possible if a mixed col- Damp down, shade if required and check that gardener who may have to be away all day. areas where air pollution is low. This consider
lection of plants is grown, for plants have there are no dry plants (but leave the main Happily, it can be modified and compromises ably cuts down light intensity, the effects of
differing needs. In theory at least, the fully watering operation until later). In early after- made. Full ventilation and essential watering which are particularly noticeable in winter.
automated greenhouse can be programmed noon, go over the watering thoroughly and can be carried out just before leaving in the Plants which need good light, such as tomato,
to provide the correct levels of heat, light, damp down again if conditions are hot. If it is morning and the main watering and damping lettuce and freesia, look thin and pale and
humidity and ventilation whatever the con- not particularly hot, damp down in late after- down done on arriving home. Damping down lack substance.
ditions in the outside world. But in practice noon. As soon as direct sunlight is off the during the day, while desirable for most
this is rarely the case. Freak weather con- greenhouse the blinds can be rolled up and plants, is not essential. Automatic watering Class should be washed thoroughly in
ditions, a breakdown of equipment or a when the temperature drops back to about and ventilation help to optimize conditions autumn, using a suitable non-toxic detergent
simple power failure can quickly upset the five degrees above minimum, shut down in greenhouses left unattended during the Where the glass overlaps, dirt accumulate-
automated system. In the end, it is the skill the ventilators. During a warm spell the day. and algae flourish, forming a dark band.
of the gardener that counts. Automatic temperature may not drop so low even after Remove this dirt with a metal plant label
equipment can at best work to only fairly nightfall and the greenhouse can then be left In the winter a daily check over in the or a sliver of sheet metal. Class washing
wide tolerances and has the disadvantage of open day and night. Ail depends on the morning or evening is enough. If automatic should be carried out at intervals during
providing the same levels of water, heat and minimum temperature being maintained. ventilators and capillary watering are in- the winter, especially in areas of air pollution.
so on for all the plants in the greenhouse. It stalled, then a weekly check over should At other times of the year it is usually not
is most important to get to know the limita- Cleaning the greenhouse suffice in winter.
tions of the individual greenhouse and the
degrees of tolerance of the plants being
grown. This knowledge goes to build up the
intuitive skill which all good growers have, to
know when to water and ventilate, when to
damp down, shade or feed for the very best
results. All this takes patience and practice
and the beginner must be keen enough to
spend time with his plants, noting what
happens to them under different conditions.
Record keeping There is much to be said for
keeping a greenhouse diary or notebook.
Record in it the daily maximum and minimum
temperatures, when seeds are sown or cut-
tings taken, when plants are potted, fed,
staked, and stopped. In addition, comments
can be made from time to time on the
vigor, appearance and health of the plants.
Over the seasons, a valuable record of the
prevailing conditions is built up.

The daily routine In late summer, scrub the framework of the In autumn, wash the glass thoroughly using At the same time, scrub surfaces such as
It is important to establish a regular daily greenhouse to remove pest and disease a non-toxic detergent. Remove dirt and paths and walls to remove algae, using a
routine when gardening under glass. To fail organisms. First empty the greenhouse. Use algae from glass overlaps with an alloy dilute solution of a proprietary algicide.
to do so is likely to lead to the disappoint- a dilute sterilizing agent. plant label.
ments of poor-quality plants and frequent
failure of seedlings and young plants.

Introduction/Hygiene 2

so important and in summer the layer of of soil or chemicals around the insides of the PEST AND DISEASE CONTROL Apply fumigants in the evening, then leave
grime can even he beneficial, acting as pots. Soak clay pots in water to ensure Good greenhouse hygiene, as outlined in the the greenhouse closed overnight. Seal any
partial shading, cleanliness. Perhaps the chief cause of infec- previous section, is an essential starting point leaks and close all ventilators before applica-
tion of soil-borne rots is the use of dirty in the avoidance of pests and diseases. How- tion. To sterilize the greenhouse, empty it of
At least once a year the framework of the containers for propagation. It is of great im- ever, problems will inevitably occur because plants and burn sulfur at the rate of 1 lb per
greenhouse should be scrubbed to remove portance to ensure that containers are clean. it is impossible to avoid introducing infected 1000 cu ft. The burning sulfur produces sul-
pest and disease organisms such as the eggs material into the greenhouse. The following fur dioxide gas, which is highly poisonous.
of red spider mite and spores of fungal In order to avoid cross-infection, always pages detail pests and diseases met with in Leave the greenhouse as soon as the sulfur
diseases. To do the job properly the green- remove containers and used soil from the the greenhouse and prescribe remedies. On is ignited.
house should be empty so that a sterilizing greenhouse when not in use. Spent soil pro- this page methods of control are discussed.
agent, a chemical fluid, can be added to the vides ideal conditions for the multiplication Biological control
washing water. Late summer is a good time to of both damping off fungi and sciarid flies. Control methods In the open, many harmful pests are kept
wash the greenhouse, when all but the It is important to wipe tools clean after use Because the greenhouse is a closed environ- under control by predators such as birds or
tenderest plants can be stood outside. to ensure they do not become a potential ment it is often easier than in the open other insects. In the closed greenhouse
source of infection. garden to control pests and diseases. Some environment, such natural balances break
In a humid greenhouse a film of green algae pests, such as snails, can be removed by hand, down, leading to pest problems. In an effort
can form on all moist surfaces including walls It is futile to go to great lengths to sterilize but most greenhouse problems will have to to avoid over-use of chemicals, biologists
and floors, and can become slippery. All such soil, or to go to the expense of buying sterile be dealt with by chemical means. Some bio- have investigated the possibility of biological
surfaces should be scrubbed, using one of the soil mixes, if they are left lying about open to logical control is possible for a few green- control. This means introducing a predator to
proprietary algicides in the water. the elements. All mixtures and their com- house pests (see below). Good growing prac- attack concentrations of harmful pests. Some
ponents should be kept bagged and covered tice is the first line of defence, for healthy predators have been found to be regularly
Hygiene should not stop at keeping the to maintain their reliability. Do not attempt sturdy plants are less susceptible to disease effective and are available commercially. A
greenhouse clean. All used pots and seed to re-use spent soil mixes, even if sterilized, than sickly ones. predatory mite, Phytoseiulus persimilis, con-
flats should be thoroughly washed and as the chemical balances will be out of trols greenhouse red spider mite. A ladybird,
scrubbed before re-use to minimize the proportion. Applying chemicals Choose a chemical Cryptolaemus montrouzeri, can be used
spread of disease. Remove any "tide-marks" which will not harm the plants being grown, against mealybugs; a parasitic wasp, Encarsia
kept in a bin with a tight-fitting lid to avoid but which is effective against the problem formosa, for greenhouse whitefly; and a
After use, wash and scrub seed boxes and staleness and possible contamination. concerned. Remove any plants likely to be bacterium, Bacillus thuringiensis, attacks
pots to minimize the spread of disease. Remove spent soil from the greenhouse harmed by the chemical, or cover them with caterpillars.
Store containers neatly and do not allow after use. plastic sheeting secured with string or elastic
debris to build up. Potting soil should be bands. Carefully follow the instructions given If biological control is used chemical means
on the next page for the use of chemicals in must be ruled out until the predators have
the greenhouse. When spraying, open all had a chance to work, which limits its applica-
ventilators and the door. Many pesticides are tion if more than one pest is found. Predators
also available as dusts which are applied from are a cure rather than a prevention: they
a puffer pack. Use dusts on flowers and on cannot work until their prey, the pest, is
plants sensitive to moisture on foliage. present. The critical time to introduce preda-
Fumigation Chemicals can also be applied in tors is when the pest first appears. The preda-
smoke form, a process called fumigation. tor can then breed and build up a large
First check carefully that none of the plants enough population to eradicate the pests.
present will be damaged by the fumigant to Predators will only breed faster than the
be used. The manufacturer's instructions will pests when the daytime temperature exceeds
contain a list. Remove any such plants from 21°C/70°F and light intensity is good.
the greenhouse. Fumigants are available as
simple pyrotechnic smokes which resemble While biological control avoids chemical
slow-burning fireworks, or as solids which are build-up on plants, a point especially to be
vaporized on electric elements. Fumigants borne in mind with food crops, it is a less
should be applied at a measured rate depend- certain and more complicated method of
ing upon the cubic capacity of the green- pest control than the use of chemicals. The
house. Measure the capacity by the formula use of predators has to be carefully timed.
length x breadth x average height. Fumiga- This may involve investigating sources of
tion can be used against specific pests or as a supply well before the trouble is likely to
general hygiene measure every six months. arise and taking swift action once the pests
are noticed.

Pests and diseases 1

Introduction SEEDLINGS Plant wilting caused by over- or under-watering or malnu-
This section is concerned with the various This section covers the period of plant growth Bacterial wilt (Xanthomonas begoniae) trition; prevent it by maintaining even growth
pests, diseases and disorders that may affect between germination and the emergence of causes wilting and spotting on leaves of through good cultural treatment.
plants grown under glass. It is divided into true leaves. winter-flowering begonia hybrids derived
two parts: ornamental plants, and fruits and from B. socotrana and 6. dregei. Burn severely Leaves distorted
vegetables. Within each part, the possible Seedlings eaten diseased plants and do not propagate from Tarsonemid mites are a group of tiny
troubles are listed by symptom, such as Slugs, woodlice and millipedes can destroy them. If they are only slightly diseased, cut creatures that infest the growing points of
Leaves discolored or Stems galled. Under plants by eating the foliage before the seed- out affected parts and decrease the tempera- certain greenhouse plants. The bulb scale
each symptom the various causes that may lings have a chance to become established. ture and humidity of the greenhouse. This mite (Steneotarsonemus laticeps) lives in the
produce it are described and control measures Slugs are the most destructive; woodlice and will reduce the spread and severity of the neck of narcissus and hippeastrum bulbs.
suggested. millipedes only become troublesome when disease, but it will also delay flowering. It causes a distinctive sickle-shaped cur-
thev are present in large numbers. Slug Disinfect the greenhouse after a severe vature of the leaves and a saw-toothed
The most important means of controlling pellets containing metaldehyde give some attack of the disease. notching along the margins. The flower
pests and diseases is by good cultural prac- additional protection against woodlice and stems become stunted and distorted, again
tice. In particular, ensure that plants are not millipedes. Scatter pellets along seed rows. Leaves discolored with a saw-toothed scar along the edges of
allowed to become pot-bound or suffer from Leaf scorch (Stagonospora curtisii) causes the stem. The cyclamen mite (Tarsonemus
malnutrition, that they are given sufficient Seedlings collapsing brown blotches to appear on the leaves of pallidus) and broad mite (Polyphagotarson-
water and light, and that the greenhouse has Damping off is usually due to species of the hippeastrum (amaryllis), particularly at the emus latus) live inside the leaf and flower buds
the correct temperature and humidity for the soil- and water-borne fungi Phytophthora leaf bases, and also on the flower stalks and of plants such as cyclamen, Hedera (ivy),
plants. If any of these conditions is unsuitable, and Pythium. Seedlings of antirrhinum, sweet petals. The affected tissues usually rot begonia, impatiens, saintpaulia and Sin-
the plants will not only be much more sus- peas, lobelia, stock and zinnia are particularly and become slimy. Cut out such tissues and ningia (gloxinia). Their feeding causes stems
ceptible to attack by pests and diseases, they susceptible to infection, and collapse at burn them. Spray or dust affected plants with and leaves to become scarred and frequently
may also be damaged by the condition itself ground level. Prevent infection by sowing sulfur or zineb. to be distorted into spoon-like shapes. The
and develop recognizable symptoms. Such thinly, since the disease is encouraged by Unsuitable cultural conditions can check the growing points may be killed and the flowers
problems are known as physiological dis- overcrowding, and by using sterilized soil or growth of hippeastrums, causing red blotches are either distorted or fail to develop. There
orders. They are discussed under the appro- compost of a good tilth. Over-watering can or streaks (or both) to appear on the leaves, are no controlling chemicals available to
priate symptom. also induce damping off, so water carefully flower stalks and bulbs. This trouble is usually amateur gardeners. Burn all infested plants.
with clean water. Give adequate light but
Even if plants are given the correct growing not too much heat. Check slight attacks by
conditions, pests and diseases will still occur watering with captan or zineb after removing
occasionally, and in this case it is often all dead seedlings. Captan or thiram seed
advisable to use pesticides or fungicides. dressings can help prevent damping off
Such chemicals are, however, potentially disease.
dangerous and must be handled with care at
all times; failure to do so may harm the user BULBOUS PLANTS
or damage plants. It is particularly important This section treats problems that are specific
that the manufacturer's instructions are read to plants having bulbs, corms, tubers or
and followed, and that all chemicals are rhizomes.
stored in a cool dark place away from food-
stuffs, if possible in a locked cupboard where Plant stunted
children and pets cannot reach them. Wear Non-rooting of hyacinth bulbs is a physio-
rubber gloves when diluting chemicals, and logical disorder, the precise cause of which
thoroughly wash the sprayer, gloves and any is not known. The leaves do not develop at the
other equipment after use. Always spray normal rate and the inflorescence remains
from all sides of the plant to give an even stunted. The roots of an affected bulb are
coverage and ensure that both upper and either lacking or poorly developed. This
lower leaf surfaces are covered. Finally, avoid problem can be caused by the temperature
using insecticides on plants that are in flower being too high during storage or forcing, or
since the petals may be damaged. by forcing or lifting too early. Unfortunately
it is not possible to detect in advance those
Plants that have been severely attacked by bulbs in which the non-rooting tendency has
pests or diseases should not be left in the developed.
greenhouse since they can become a source
of infection for other plants. All such plants
should, if possible, be burned.

Pests and diseases 2

Leaves, flowers and bulbs rotting Bulbs, corms or tubers rotting storage but when the corms are replanted these caterpillars eat holes in the foliage.
Soft rot (Erwinia carotovora var carotovora) Basal rot may be caused by various fungi, the rot progresses rapidly. Destroy badly Control light infestations by searching for and
causes a soft, slimy, evil-smelling rot of the and affects mainly Lilium and Lachenalia. The infected plants and disinfect the greenhouse. squeezing the caterpillars' hiding places.
leaves and bulbs of hyacinths. It often com- roots and base of the bulb rot, resulting in Sterilize the soil where diseased plants have Otherwise spray the plants thoroughly with
mences in the inflorescences when florets stunting of the top growth and discoloration been growing in beds. Examine corms when a dilute solution of trichlorphon when signs
have withered through a physiological dis- of the leaves. Discard badly affected bulbs. removing them from store and cut out any of damage are seen. Other caterpillars that
order known as blindness; for details see In less severe cases cut out diseased roots brown areas. Then steep them for two hours can be found on greenhouse plants include
right under Buds withering. If the rot has not and tissues, or scales in the case of lily bulbs. in a 2 per cent formalin solution before those of the angle shades moth (Phlogo-
advanced too far it may be possible to save Then dip the bulbs in a solution of captan or planting them out. phora meticulosa) and the silver-Y moth
the bulbs for planting outside by cutting out benomyl before re-potting. Prevent such (Autographa gamma). These feed in the open
all infected tissue. Such bulbs planted out- troubles by using only sterile compost and Inflorescence loose on the foliage and flowers but may be
side will not flower for a year or two. clean pots. Loose bud of hyacinth, in which the stem difficult to find since they are active mainly at
below the flower bud fractures completely at night. Control these pests by hand-picking or
Roots or tubers eaten Begonia tuber rot and cyclamen corm rot an early stage of growth, is usually caused by by applying the above insecticides.
Vine weevil grubs (Otiorhynchus sulcatus) are usually occur as a result of frost damage dur- storing bulbs at too low a temperature. Slugs (various species) can damage most
plump white maggots about 1/2 in long with ing storage. The tissues become soft and Bulbs that have been moved from cold plants, especially during the early stages of
light brown heads. Plants grown from tubers have a sweetish smell. Prevent these rots by storage into a very warm place are parti- growth. They frequently leave a slime trail on
are particularly susceptible but many other ensuring that tubers and corms of the cularly susceptible. Loose bud may also be the foliage, which distinguishes their damage
plants may be attacked. Usually the first respective plants are stored carefully in a caused by incorrect lifting or forcing. Unfortu- from that caused by caterpillars. Control
symptom that is noticed is the plant wilting frost-proof place. nately it is impossible to detect the tendency them by scattering slug pellets based on
and, when it is tipped out of its pot, most of for loose bud in a consignment of bulbs. metaldehyde onto the soil surface around
the roots are seen to have been destroyed. Arum corm rot {Erwinia carotovora var caro- the plants.
Such plants rarely recover. Badly affected tovora) can be serious wherever arums Buds withering
plants should be destroyed, the soil thrown {Zantedeschia spp. and hybrids) are grown Blindness of bulbous plants is usually caused Leaves discolored
away and the pot sterilized. Some protection under glass in large numbers. The plants by the soil being too dry at a critical stage of Faulty root action may be caused by over- or
is given by adding chlorpyrifos granules or wither and collapse due to rotting of the growth. Prevent this by making sure that the under-watering, malnutrition or poor pot-
naphthalene flakes when potting up. corms; these may develop extensive brown compost never dries out. Less frequently it is ting. It results in irregular yellow or brown
areas with rotting roots arising from them. caused by storing bulbs before planting in blotches on the leaves, or complete dis-
The corm lesions can lie dormant during conditions that are too hot and dry. Prevent
this either by potting up immediately on SOOTY MOLD
obtaining bulbs, or by storing them in the
proper conditions. The flower buds of affected Some sap-feeding insects such as aphids,
bulbs turn brown and wither at an early whiteflies, scales and mealybugs excrete a
stage. Such bulbs can be planted out in the sugary liquid known as honeydew. Since
garden but will not flower for a year or two. these insects feed mainly on the under-
sides of leaves the honeydew drops down
GENERAL PLANTS onto the upper surfaces of leaves grow-
The pests and diseases mentioned in this ing below the actual infestation. Such
section may, unless otherwise stated, affect leaves become sticky, and under damp
any type of plant, including those with conditions various black, non-parasitic
bulbs, corms, tubers, or rhizomes. fungi known as sooty mold rapidly de-
velop. They do not directly harm plants
Leaves eaten because they grow on the honeydew,
although the amount of light and air
Carnation tortrix caterpillars {Cacoecimor- reaching the foliage is reduced. Remove
pha pronubana) feed on a very wide range of sooty mold by wiping the leaves with a
plants and can be found throughout the year soft damp cloth. Good ventilation makes
in heated greenhouses. The "caterpillars grow the atmosphere drier and thus less suitable
up to 3/4 in long and are pale green with brown for the growth of sooty mold, but the
heads. They fold over the edge of a leaf with best cure is to identify and control the pest
silken threads, or bind two leaves together, that is producing the honeydew.
and when small feed unnoticed by grazing
away the inner surfaces of these leaves. Later

Pests and diseases 3

coloration of the foliage, and premature leaf- Glasshouse thrips (Heliothrips haemor- control eelworms, and infested plants should Leaves with visible fungal growth
fall. Prevent such troubles by careful potting rhoidalis) are thin yellow or dark brown be burned. However, it is possible to give Powdery mildews are common on chrysan-
up and correct cultural treatment for the insects about 1/10 in long that live mainly on chrysanthemum stools a hot water treat- themums, begonias and cinerarias, and occur
type of compost being used. Applications of the upper surfaces of leaves and on flowers. ment so that they will subsequently produce occasionally on other plants. The symptoms
foliar fertilizer should help overcome the They feed by sucking sap and cause a full cuttings free of eelworms. Wash the dormant are white powdery spots on the leaves and
troubles, but in severe cases it may be neces- green or silvery discoloration of the foliage, stools free of all soil and then plunge them sometimes the stems. Ventilate the green-
sary to re-pot the affected plant. which is also marked by minute black spots in hot water at 46°C/115°F for five m i n u t e s - house well since the fungi are encouraged by
Tip scorch of the leaves of plants such as caused by the thrips' excretions. Control this it is important that the time and temperature a humid atmosphere. Plants that are dry at
aspidistra, chlorophytum and sansevieria pest by spraying thoroughly with a pyre- are exact. Then plunge into cold water. the roots are more susceptible to infection,
may be caused by the air being too hot or throid compound, derris, malathion or a so water before the soil dries out completely.
dry, or by faulty root action (see above). systemic insecticide. Leaves mined Fumigate the greenhouse with dinocap
Affected plants should recover once the Chrysanthemum leaf miner grubs (Phyto- smokes or spray with dinocap or benomyl.
scorched leaves have been removed and the Leaves with corky patches myza syngenesiae) tunnel the leaves of Remove severely affected leaves.
correct cultural treatment given. In the case Oedema, or dropsy, is caused by the atmos- chrysanthemum and related plants such as Rusts can affect chrysanthemums, fuchsias,
of saintpaulia, anthurium and palms such as phere being too moist or the soil too wet. It cineraria (Senecio cruentus hybrids) and ger- pelargoniums, cinerarias and carnations. On
kentia, it may be necessary to place the pot in shows as pale pimple-like outgrowths on the bera. These mines show on the leaves as fuchsias and cinerarias orange powdery
a larger container packed with damp moss or undersurfaces of the leaves and on the stems. whitish-brown lines meandering through the pustules develop on the leaves, predomi-
peat in order to create a humid atmosphere. The outgrowths later burst and then become leaf and, in heavy infestations, leaves may nantly on the lower surfaces. On other plants
Sun scorch of leaves usually shows as pale brown and powdery or corky. The most sus- lose almost all their green color. A single the pustules produce masses of chocolate-
brown blotches (often elliptical) across the ceptible plants are eucalyptus, ivy-leaved application of benomyl pirimiphos-methyl colored spores. Remove arrd burn affected
foliage. It is caused by the sun's rays on a hot pelargonium, peperomia and camellias— controls this pest if applied as soon as mining leaves. If severely infected, destroy the plant.
day passing either through glass onto moist the last mentioned develops large scabby begins, but if the plants are badly infested Reduce the humidity of the atmosphere, and
foliage, or through a flaw in the glass which patches on the undersurfaces. Improve the three applications of insecticide at ten day avoid wetting the leaves. Spray at seven to
acts as a lens to intensify the rays. Prevent cultural conditions by careful watering and intervals will be necessary. ten day intervals with zineb or mancozeb.
scorch in greenhouses by careful ventilation by ventilating the greenhouse. Do not re-
to reduce humidity. move affected leaves since this will only make
matters worse.
Leaf spots are caused by a variety of fungi. In
practically all cases they produce brown or Corky scab of cacti is caused either by a lack
black spots on the leaves, but on some hosts of light and the humidity being too high, or
the spots have a purple border or they may by over-exposure to sunlight. It occurs most
have pinpoint-sized black dots scattered frequently on Epiphyllum and Opuntia and
over them. Remove affected leaves and spray shows as irregular rusty or corky spots which
with mancozeb or zineb. If further trouble develop into sunken patches as the tissues
occurs the plants may be lacking in vigor due beneath die. Where the trouble is very un-
to faulty root action, in which case see above sightly propagate from the affected plant and
and previous page. ensure that new plants are given correct
cultural treatment and are not exposed to
"Ring pattern" on saintpaulias and achimenes too much light.
is caused by a sudden chilling of the leaves
from watering overhead in sunlight. Affected Leaves blotched
leaves develop large yellow rings. Prevent Chrysanthemum eelworm and fern eelworm
this by careful watering. (Aphelenchoides ritzemabosi and A. iragariae)
Viruses such as tomato spotted wilt and are microscopic worm-like animals that live
cucumber mosaic affect a wide range of inside leaves. Many different plants may be
plants. In general the symptoms are mottled, infected, although in greenhouses the main
blotched or striped leaves, affected parts hosts are those indicated by the pests' com-
being pale green, yellow or black. The mon names. Infested parts of the leaves turn
leaves may also be distorted and the plants brown. At first these areas are clearly separ-
stunted. Destroy any plant showing these ated by the larger leaf veins from the green,
symptoms. A valuable plant such as an healthy parts, but eventually the brown areas
orchid may be kept but it will always produce coalesce and the whole leaf dies. None of the
discolored leaves and the trouble may spread chemicals available to amateur gardeners
to previously healthy plants.

Pests and diseases 4

Leaves with pests visible and the top growth wilts or collapses. Prevent the latter have yellow-brown, flat, oval shells yellow insects, about 1/10 in long, that suck
Greenhouse whitefly (ltrialeurodes vapor-iro- these diseases by using sterilized soil mixes of the same length. The insects live under- sap from the petals of carnation, chrysan-
rum is one of the most common and and pots, and by using clean water. Pot up neath these shells and feed on sap. Once themum, cyclamen and other plants. The
troublesome of greenhouse pests. for details, carefully and tease out the roots of pot- a suitable feeding place is found they do not petals develop white flecks where the thrips
sec page 40. bound plants. Control by watering with move. Control by spraying plants thoroughly have fed. Control them by spraying thorough-
Peach-potato aphid and mottled arum aphid ethazol plus benomyl, or use a solution of with malathion or nicotine three times at two ly with malathion or nicotine. Care needs to
(Myzus persicae and Aulacorthum circum- Banrot as a soil drench. In severe cases re- week intervals. be taken since flowers may be marked
llexum) are both species of greenfly that suck pot, using a smaller pot if necessary, in sterile Mealybugs (Pseudococcus spp.) are gray- by insecticides, so spray when the plants
sap from a wide range of plants. For details, soil or potting mixture after having removed white soft-bodied insects that grow up to 1/4 in are not exposed to bright sunlight or high
see page 40. all dead parts including roots. Spray the long. They infest cacti, succulents and many temperatures.
Soft scales (Coccus hesperidum) are sap- developing leaves with a foliar fertilizer. other plants, and secrete white, waxy fibers
feeding insects that live on the stems and Gray mold (Botrytis cinerea) causes plants to that cover the mealybug colonies and their Viruses such as cucumber mosaic and
undersides of leaves near the main veins. For decay and affected leaves and flowers to egg masses. Control them by spraying with tomato spotted wilt can cause spotting or
a description of these pests and their control, become covered with a gray-brown mass of malathion or nicotine. Thorough applications streaking of flowers, which may also be dis-
see below. fungal spores. The petals may also develop are necessary because mealybugs tend to torted. Most frequently affected are chrysan-
numerous small red or brown spots. Cray live on relatively inaccessible parts of the themums and bulbous plants, especially
Leaves mottled mold spores are always present in the air plant, and two or more sprays at two week lilies and cyclamen. Destroy affected plants.
Greenhouse red spider mites (Tetranchus and infect plants through wounds and dead intervals may be needed. On plants that are
urticae) are minute pests that attack most or dying tissue. Infections can also occur liable to be damaged by insecticides, such as Flowers spotted or rotting
greenhouse plants. For details, see page 40. between diseased and healthy tissues. Pre- Crassula and ferns, dab mealybugs with a Gray mold (Botrytis cinerea) frequently attacks
Greenhouse leafhoppers (Zygina pallidifrons) vent gray mold by good hygiene and by brush dipped in methylated spirit. the flowers of cyclamen and chrysan-
suck sap from the undersides of leaves and removing dead leaves and flowers promptly. themums. For symptoms and treatment, see
cause white, pinhead-sized dots to appear on Ventilate the greenhouse carefully to reduce Stems galled under Stems or crowns rotting, above.
the upper surfaces. In heavy attacks these humidity, and water early in the morning and Leafy gall (Corynebacterium tascians) affects
dots coalesce and most of the leaves' green not at night. Once the disease has appeared mainly pelargoniums and chrysanthemums, Pests in or on the soil
color is lost. Adult leafhoppers are about on any type of plant, spray with benomyl or and shows as a mass of abortive and often Vine weevil grubs (Otiorhynchus sulcatus)
5/8 in long and pale yellow with two V-shaped a copper fungicide or use Isotherm Termil fasciated (flattened) shoots at soil level. are plump white legless grubs, up to 1/2 in long,
gray markings on their back. The nymphal bombs. In the case of cyclamen affected by Destroy affected plants and sterilize pots and with light brown heads. For symptoms of
stages are creamy-white. As they grow they gray mold around the crown, dust with the greenhouse bench on which the plants attack, and treatment, see under Roots and
periodically shed their skins, which remain captan. were standing. Do not propagate from dis- tubers eaten in the Bulbous plants section.
attached to the undersides of the leaves. eased plants. For details of sterilizing, see Fungus gnats or sciarids (various species) are
Control leafhoppers by spraying with any of Carnation wilt is caused by the fungi Verti- page 33 on Hygiene. small gray-black flies that run over the soil
the insecticides malathion, pirimiphosmethyl, cillium albo-atrum and Fusarium oxysporum surface of pot plants or fly slowly around
methoxyclor or a pyrethroid compound. f dianthi. Affected plants wilt rapidly and the Flower buds dropping them. Their larvae are thin white maggots up
leaves become either yellow or gray-green Bud drop affects stephanotis, gardenias, to 1/4 in long with black heads. They live in the
Stems or crowns rotting and then straw-colored. In both cases a hibiscus and camellias. It is caused by the soil soil and feed mainly on rotting plant material
Blackleg (various organisms) affects pelar- brown discoloration can be seen in the inner being too dry at the time the buds were but they sometimes damage the roots of
gonium cuttings and sometimes the mature tissues of affected stems. Prevent these beginning to develop. Prevent this trouble seedlings and plants that are in poor health.
plant. The stem bases become soft, black diseases by using sterilized pots and soil. by ensuring that the soil never dries out. They may also tunnel into the base of soft
and rotten, and affected plants die. Prevent Destroy severely affected plants and sterilize Gardenias may also lose their buds if the cuttings and cause them to rot. Control the
this disease by using sterile soil mixes and the greenhouse bench or floor on which the atmosphere is too dry. Prevent this by adult flies by spraying with a pyrethroid
pots, and by hygienic cultural conditions, plants were standing. Do not propagate syringing the plants in the morning and compound. Against the larvae, mix some
including the use of clean water. Destroy from diseased plants. To reduce the spread evening during warm sunny weather except diazinon granules into the soil around the
severely diseased cuttings, but in the case of of wilt drench the remaining plants with a when the flowers are open, otherwise they plants.
valuable plants it may be possible to propa- solution of benomyl or thiophanate-methyl, will discolor. Over-watering can also cause
gate by taking a fresh cutting from the top of repeating the treatment two weeks later. bud drop of gardenias. Bud drop can be Springtails (various species) are white soil-
a diseased plant. avoided by careful greenhouse management. dwelling insects, about 1/10 in long. They are
Stems or crowns with pests visible Ensure that temperature, humidity and venti- found especially in peat-based mixes, and
Foot, crown and root rot may be caused by Scale insects such as hemispherical scale lation are correct. are distinguished by their habit of jumping
black root rot fungus or other soil or water- (Saissetia coffeae) and soft scale (Coccus when exposed on the surface of the soil. They
borne fungi. These organisms cause a brown hesperidum) encrust the stems of many Flowers discolored usually appear on the soil surface after plants
or black rot of the tissues at the base of the different plants. The former have red-brown Thrips (various species) are thin, black or have been watered. However, they cause no
stems, around the crowns or at the roots, convex shells about ^ in in diameter, while damage and there is, therefore, no need for
any controls.

Pests and diseases 5

Leaves discolored dirty tanks and butts. give adequate light but still produce good crops it the deficiency is HORMONE WEEDKILLER DAMAGE
Downy mildew of brassica seedlings, especi- not too much heat. Check slight attacks by corrected early on.
ally cauliflowers, is caused by the fungus watering with captan or zineb after removal This commonly affects plants under glass,
Peronospora parasitica and that of lettuce by of the dead seedlings. Leaves moldy particularly vines and tomatoes. Affected
Bremia lactucae. White mealy or downy tufts Wirestem fungus, caused by Rhizoctonia Tomato leaf mold (Cladosporium lulvum) leaves become narrow and fan-shaped,
of fungal growth develop on the underside of solani, is a disease of brassica seedlings, affects only tomatoes grown under glass or show parallel veins, are frequently cupped
the leaves, which become blotched on the particularly cauliflowers, but the same fungus polyethylene. A purple-brown mold develops and the shoots twist spirally. Take care
upper surface. Affected seedlings are severely can also affect seedlings of other vegetables. on the lower surface of leaves which show when using hormone weedkillers, apply
checked and lettuces may later be attacked Stems of affected brassica seedlings shrink yellow blotches on the upper surface. These ing them with equipment kept solely for
by gray mold (see below). These mildews are at ground level before they topple, but other symptoms may be overlooked as affected their use. Do not use them on a windy day
most troublesome on overcrowded seedlings seedlings damp off as described above. Let- leaves are subsequently often attacked by and, when spraying nearby, close green-
growing in very humid conditions. Prevent tuce seedlings affected by this fungus usually gray mold. Grow resistant varieties and keep house ventilators. Do not store weed-
the diseases by sowing seed thinly in steril- succumb to gray mold (see below) fairly the greenhouse temperature less than 21°C/ killers in a greenhouse since vapors from
ized, well drained soil or seed sowing mix, and soon afterwards so that the original cause 70°F. Ventilate well since the disease is them can affect plants. Wash hands and
ventilate carefully to reduce humidity. Do not may be overlooked. Prevent by sowing encouraged by humid atmospheres. At the tools after applying weedkillers.
over-water seedlings. Should mildew occur, thinly in a good tilth and avoid over-watering. first signs of trouble spray with benomyl or
remove diseased leaves and spray with Use sterilized soil or a good-quality soilless mancozeb or use Exotherm Termil every (see above). The top growth wilts or collapses
mancozeb or zineb. On brassica seedlings, mix to help prevent infection. The fungus is 7 days. completely because these soil: and water-
chlorothalonil and captafol may be used. not controlled by fungicides with the excep- borne organisms attack the roots and stem
tion of dicloran. The chemical can be raked Leaves and stems rotting bases. Prevent this by the use of clean water
Stems collapsing into the soil before sowing seed where this Gray mold (Botrytis cinerea) is a c o m m o n and by changing or sterilizing the soil at
disease is known to be troublesome. problem under glass, affecting particularly least once every three years, or by the use of
Damping off is usually due to species of the grapes, strawberries, cucumbers and tom- sterile soil. Plant carefully, and tease out
soil- and water-borne fungi Phytophthora DISEASES OF MATURE CROPS atoes. Lettuce tends to wilt due to attack at roots of pot-bound plants. Do not over- or
and Pythium. Seedlings of lettuce, tomato, The diseases described below may affect any ground level. Affected stems, fruits and leaves under-water as plants suffering from faulty
mustard and cress are most susceptible to crop, fruit or vegetable, being grown in rot and become covered with a gray-brown root action (see above) are very susceptible
infection, and collapse at ground level. Over- greenhouses, cold or heated frames or under velvety fungus growth. Sometimes the fungus to attack. If foot rot occurs, water with a
crowding encourages the disease, therefore cloches, unless otherwise stated. Vines and does not rot tomato fruits but produces pin- solution of captan, or alternatively, zineb,
sow thinly and use sterilized soil of a good peaches are treated separately at the end of point spots, each with a pale green ring, or dust at the base of the plant with dry
tilth or a well-prepared sterilized sowing mix. this section. known as water spots, which can still be seen bordeaux powder. When tomatoes are
The organisms that cause damping off are on ripe fruit. Spores of the fungus infect plants affected, place fresh sterilized soil around
often present in unsterilized soil, particularly Leaves discolored through wounds and dead and dying tissues, the base of the stems and spray all plants
if it is compacted causing poor aeration. Faulty root action is due to over- or under- or by contact between diseased and healthy with a foliar fertilizer to encourage the
Overwatering can also induce damping off. watering or poor transplanting and can cause tissues. Remove dead leaves and over-ripe development of new roots in the fresh soil.
Use clean water to prevent infection by irregular yellow or brown blotches on the fruits promptly to avoid infection. Ventilate As these new roots develop they should re-
water-borne organisms which build up in leaves. Prevent this by careful planting and greenhouses carefully to reduce humidity vitalize the plants.
correct cultural treatment. Applications of a and water early in the morning, not at night.
foliar fertilizer should help to overcome the Over-watering plants should be sprayed Verticillium wilt is caused by species of the
trouble, but with severely affected tomatoes with thiram every three or four weeks. fungus Verticillium. The larger leaves wilt
it may be necessary to mound sterile soil Prevent infection of grapes and strawberries during the day, particularly on hot days, but
around the base of the stem into which new by spraying with benomyl as the first flowers recover at night. Affected plants may lose
roots can grow as the plant recovers. open, repeating twice at ten day to two week their older leaves. Brown streaks are seen
Magnesium deficiency is common on tom- intervals, or with captan or thiram except running lengthways in the tissues if the base
atoes and eggplants. Orange-yellow bands on fruit to be preserved or canned. Fumigate of the stem is cut longitudinally. Destroy
develop between the veins on the lower an affected greenhouse with smokes if badly affected plants. Prevent the disease by
leaves, which gradually turn brown as the possible. using sterilized soil or planting mix, and
symptoms spread progressively upwards. always plant verticillium and fusarium re-
Spray at the first signs of trouble with 1/2 lb Stems wilting sistant varieties. Seed catalogs indicate which
magnesium sulfate in 21/2 gal of water, to Foot and root rot can be due to various fungi, varieties are resistant.
which is added a spreader. Spray repeatedly including Thielaviopsis basicola and species
every seven to ten days until the plants have of Fusarium, as well as those fungi which Tomato stem rot {Didymella lycopersici)
completely recovered. Affected plants can cause damping off and wirestem of seedlings causes a sudden wilting of mature plants.
A brown or black canker develops on the

Pests and diseases 6

stem, usually at ground level, and small black Chats (small tomato fruits) may form on by adequate and early ventilation, by ensur- VINES
specks, which are the fruiting bodies of the plants which are dry at the root, but poor ing that plants have sufficient shade, and by The most serious disorder to affect vines
fungus, can just be seen with the naked eye all pollination caused by cold nights and a dry correct feeding and watering. Crow tomato grown under glass is powdery mildew.
over the diseased tissues. These produce atmosphere may also be responsible. Encour- varieties resistant to greenback. Consult seed
many spores which over-winter and act as a age pollination by syringing the foliage in the catalogs for lists of tomato varieties resistant Leaves, shoots and fruits with fungal growth
source of infection the following season. It is morning and again during the day when the to greenback. Powdery mildew (Uncinula necatof) shows a
essential, therefore, to burn all debris and to weather is hot. soft white floury coating of fungus spores on
sterilize the greenhouse and equipment at the Dry set of tomatoes is also due to poor pol- Bronzing of tomatoes is caused by tobacco the leaves, young shoots and fruits. Affected
end of the season if this disease has occurred. lination. It is caused by the atmosphere being mosaic virus. Brown patches develop be- berries drop if attacked early, but in later
Destroy badly affected plants and spray the too hot and too dry. The fruits remain 1/8 in neath the surface, usually at the stalk end, attacks become hard, distorted and split,
stem bases of the rest of the crop with beno- across and become dry and brown. Syringe and give a bronzed patchy appearance to the and are then affected by secondary fungi
myl or captan. Less severely diseased plants the foliage as described for chats above. young fruit. When cut open the patches such as gray mold. Ventilate carefully since
may be saved by cutting out affected tissues show as a ring of small dark spots beneath the disease is encouraged by humidity.
and applying a paste of captan mixed with a Fruits discolored the skin. With severe infection depressed Avoid overcrowding the shoots and leaves
little water, or by painting them with a solu- Blossom end rot of tomatoes shows as a streaks which fail to ripen may radiate from and provide some heat if the greenhouse is
tion of benomyl. circular and depressed brown or green-black the stalk end. The internal tissues of such cold. Avoid also dryness at the roots. At the
patch on the skin at the blossom end of the fruits show large brown corky areas. Plants first sign of mildew spray or fumigate with
Flowers dropping fruit (the end farthest away from the stalk). In bearing bronzed tomatoes would have shown dinocap, spray or dust with sulfur, or spray
Tomato flower drop is almost always due to most cases it is due to a shortage of water at a other symptoms such as stunted growth with benomyl. Up to four applications may be
dry conditions at the roots. The flowers may critical stage in the development of young or mottled foliage earlier in the season and needed. In winter, after removing the loose
open, but break off from the stalk at the fruit. Prevent this by seeing that the soil is should have been destroyed when these bark, paint the vine stems with a solution of
joint and fall to the ground. Prevent this never allowed to dry out completely. All the symptoms first appeared. sulfur made up as follows: mix equal parts
trouble by adequate but careful watering. fruit on one truss may be affected but those of flowers of sulfur and soft soap to form
developing later should be normal if the Fruits rotting lumps the size of golf balls. Put one lump into
Fruits failing to develop normally plant has a good root system and is looked Gray mold (Botrytis cinerea) can attack a jam jar with a little water and stir well with
Withering of young cucumbers starting at after carefully. various crops. For details, see page 38. the brush used to paint the stems.
the blossom end is due to uneven growth
resulting from irregular watering. Remove all Greenback and blotchy ripening of tomatoes Fruits bitter Leaves discolored
the fruits from an affected plant to rest it, and show as hard green or yellow patches on the Bitter cucumbers can be due to an excess of Scorch is due to the sun's rays striking
spray the foliage with foliar fertilizer if a poor fruits. The former occurs on the shoulder of nitrogen in the soil or irregular growth. Avoid through glass onto moist tissues on a hot day.
color. Later-developing fruits should be nor- the fruit and the latter on any part. Both may excessive use of nitrogenous fertilizers, and It shows as large brown patches which soon
mal once the plant regains its vigor, providing be encouraged by high temperatures and a maintain even growth by watering carefully. dry out and become crisp. Prevent this by
there is no root disease present. Prevent fur- shortage of potash; greenback is also caused Since pollination of the fruit can also result careful ventilation in order to reduce the
ther trouble by watering cucumbers carefully by exposure of the shoulder to strong sun- in bitterness, grow varieties having mostly humidity, and carefully remove all the
and regularly. light, and blotchy ripening may occur where female flowers. affected leaves.
nitrogen is deficient. Prevent these troubles

Pests and diseases 7

Magnesium deficiency shows as a yellow- When shanking occurs early in the season, C O M M O N GREENHOUSE PESTS
orange discoloration between the veins, cut out the withered berries and spray the
but in some varieties the blotches may be foliage with a foliar fertilizer. Greenhouse red spider mite (Tetranychus both types often occurring together on the
purple. Later the affected areas turn brown. Splitting of berries most commonly occurs as urticae) are tiny, eight-legged creatures same plant, while the latter is yellow-green
Spray with 1/2 lb of magnesium sulfate in 21/2 gal a result of powdery mildew (see above). that can occur in large numbers on the with a dark horseshoe marking on its back.
of water plus a spreader such as soft soap However, it is sometimes due to irregular undersides of leaves. They are just visible Both types of aphid excrete honeydew
or a few drops of mild washing-up liquid. watering. Remove affected berries before to the naked eye but a hand lens is neces- upon which, in humid conditions, sooty
Repeat applications once or twice at two- they are attacked by secondary organisms sary to see them clearly. Despite their molds may grow and cause the leaves
week intervals. such as gray mold, and water before the soil common name, these mites are yellow- and fruit to blacken (see page 35). As the
dries out. green" with black markings; they only aphids grow they shed their skins, which
Leaves with small globules become orange-red in the autumn when become stuck on the leaf surface where
Exudation of small round green or colorless Scald is caused by the sun's rays striking they hibernate. Their sap feeding causes they are held by the sticky honeydew.
droplets from the leaves is quite natural and through glass onto moist tissues on a hot the upper surface of the leaves to become These skins are white and are sometimes
usually goes unnoticed. However, in the day. Ventilate carefully to reduce the humid- discolored by a fine mottling. In severe mistaken for whitefly or some other pest.
spring the transparent globules may become ity. Remove affected berries showing sunken infestations leaves dry up and the plants Control aphids by applying pirimiphos-
very noticeable on the young foliage. The discolored patches. become festooned with a silken webbing methyl or pyrethroid compounds. Use
symptoms are most obvious on plants grow- Oedema occurs when the roots of an affected produced by the mites. Maintaining a the last-mentioned if the crops are ready
ing in a very humid atmosphere and they plant take up more water than the leaves damp atmosphere helps to check this pest for eating.
indicate that the root action is vigorous and can transpire and is due to extremely moist but treatment with insecticides such as
the plant is in good health. Nevertheless, conditions in the soil, the atmosphere, or malathion or dimethoate will also be Greenhouse whitefly (Thaleurodes vapor-
ventilate carefully to reduce the humidity both. It shows as small warts or pimples on needed at seven day intervals until the ariorum) is a major pest of greenhouse
and prevent other troubles. the stalks and sometimes on the berries and pest has been controlled. Take care when plants. Both the small, white, moth-like
even on the lower leaf surface. These out- applying these chemicals to cucumbers adults and their flat, oval, white-green,
Vine dying growths may break open and then have a and melons as they may be damaged by scale-like larvae feed by sucking sap from
Honey fungus (Armillaria mellea) frequently blister-like or white powdery appearance, or insecticides. Avoid this risk by spraying in the underside of leaves. Like aphids, adults
kills indoor and outdoor vines. White fan- they may become rusty-colored and show the evening when temperatures are and larvae excrete honeydew, which
shaped growths of fungus develop beneath as brown scaly patches. Do not remove the cooler, and by making sure the plants are allows the growth of sooty mold. White-
the bark of the roots and the main stems at affected parts as this will make matters worse. not dry at the roots. As an alternative to fly eggs and immature stages are not very
and just above ground level. Dark brown Maintain drier conditions both in the air and insecticides this pest can be controlled susceptible to insecticides, making well
root-like structures known as rhizomorphs soil; with correct cultural treatment the by introducing a predatory mite, Phyto- established infestations difficult to con-
develop on the affected tissues, grow out affected plant should eventually recover. seiulus persimilis. trol. Early treatment with pirimiphos-
through the soil and spread the disease. Dig methyl or a pyrethroid compound such as
out dead and dying plants together with as PEACHES Peach-potato aphid and mottled arum pyrethrum will prevent damage occurring
many roots as possible. If the greenhouse is The following remarks on split stone also aphid (Myzus persicae and Aulacorthum if applied early. Spray heavy infestations
vacant, sterilize the soil with 2 per cent apply to nectarines. circumflexum) are both species of greenfly several times at three to four day inter-
formalin, or change the soil completely before that suck sap from a wide range of plants. vals. Greenhouse whitefly can be con-
replanting. Sterilizing is a potentially danger- Fruit failing to develop normally The former is either pink or yellow-green, trolled by introducing a parasitic wasp,
ous process. Wear gloves, protective clothing Split stone shows as a cracking of the fruit at Encarsia formosa.
and a mask. the stalk end, forming a hole large enough for
the entry of earwigs. The stone of such a fruit
Fruit failing to develop normally is split and the kernel is either rotting or
Shanking is due to one or more unsuitable absent. Affected fruits are susceptible to
cultural conditions. The stalks of the grapes secondary rotting. This trouble can be due to
shrivel gradually until completely girdled. the soil being too acid. Lime to bring the pH
Odd berries or small groups of berries then up to 6.7-7.0. Poor pollination can also cause
fail to color and develop naturally at the split stone, therefore hand-pollinate flowers
early ripening stage. The berries are watery by passing cotton-wool or a soft camel hair
and sour, black varieties turn red, white brush from flower to flower. The commonest
varieties remain translucent. Ensure over- or cause of this trouble, however, is an irregular
under-watering or stagnant soil are not re- water supply. Prevent this by watering in dry
sponsible. Reduce the crop for a year or two periods and mulching to conserve moisture.
until the vine regains its vigor. In particular, ensure that the soil is never
allowed to dry out.

Feeding and fertilizers

Plants require certain basic (hemic .lis in order general cultivation of most plants. Some plants such as cacti and alpines need very when a plant needs a nutrient boost, such as
to grow. In nature these arc present, to a plants require larger proportions of one little. Feed plants when they are growing, just before it flowers.
greater or lesser extent, in the soil, contri- element, and fertilizers are available which not when they are dormant. Plants that are Solid feeds Fertilizers in solid form—granules
buted by the base rock and by the growth provide higher concentrations of potassium suffering from over-watering, incorrect en- or powder—can be added to soil mixes.
and decay of plant and animal life. A balance for tomatoes, for example. Special formula- vironmental conditions, pests or diseases will The John Innes formulae call for the addition
between the nutrients available in a given tions are sold designed for carnations, chrys- not be cured by feeding. Establish the cause of certain amounts of John Innes base
environment and the plants that will grow anthemums and various fruits and vegetables. of the trouble and take steps to correct it. fertilizer, which is made up as a powder. Solid
soon forms and is maintained. Gardening Fertilizers containing several elements are W h e n the plant has recovered and is growing fertilizers can also be added in the form of
conditions, under glass or outside, upset this called compound fertilizers, simple fertilizers normally it will benefit from feeding. Follow top dressings to plants which are kept
balance. In the greenhouse, the plants are in a contain only one element. They are applied the feeding instructions given for individual permanently in pots. Solid feeds are also
closed environment. The only nutrients avail- when specific deficiencies are diagnosed, but crops and carefully adhere to the instruc- added to soil beds. The larger amount of
able are those in the soil and those supplied must be used with care in the greenhouse as tions on the fertilizer pack. When using rooting medium in a bed makes it possible for
by the gardener. it is easy to build up large concentrations liquid feeds, dilute to the proportions in- solid fertilizers in slow-release form to be used.
of elements in soil mixes, damaging the structed and do not use too strong a mixture. These fertilizers are specially formulated to
An explanation of the nutrient needs of plants. In addition to the three basic ele- Liquid feeding Liquid feeds are watered onto release the elements they contain over a
plants and a list of the essential elements is ments, many commercially available com- the growing medium and taken up by the period. When using solid fertilizers around
given on page 45. pound fertilizers also contain trace elements roots of plants. Because nutrients have to be plants, take care not to scorch the foliage.
needed for plant growth. dissolved before they can be taken up by the Apply the top dressing as close to the soil
Properly formulated soil mixes contain roots, application in liquid form speeds the surface as possible and water in immediately.
nutrients needed for at least the initial stages Using fertilizer process of absorption and allows the nu- Foliar feeding Some liquid fertilizers—but
of plant growth. At some point, however, While nutrients are necessary, too great a trients to reach the plant quickly. Nutrients not all—and some special compounds, can
these nutrients will become depleted and concentration can be harmful. Nutrient salts applied to the soil or a mix in a solid form be watered or sprayed onto the leaves of
more must be added in the form of fertilizer. can build up in the soil mix and damage are dissolved by water applied as irrigation plants. Foliar applications are very effective
This process is called feeding. roots. Plants must be ted at the rate they can and are then taken up by the roots. in controlling deficiency symptoms, parti-
take up food. Fast-growing crops such as cularly of magnesium and the minor elements,
Types of fertilizer tomatoes need heavy feeding, slow-growing Because liquid feeds are fast-acting, they as the elements are quickly absorbed.
Balanced fertilizers contain nitrogen, po- are applied at frequent intervals, especially
tassium and phosphorus. They are used for Foliar feeding

Applying fertilizer

1 Mix liquid or powdered fertilizer with 2 Apply the dilute fertilizer to the surface of 3 Apply top-dressings to beds, borders and Mix foliar fertilizers according to the
water in the proportions given on the pad the soil or potting mix with a watering can. large containers in granule form. Sprinkle maker's instructions. Apply to the leaves of
Do not make solutions stronger than the the granules onto the soil or potting mix the plant until run-off, using a watering can
recommended rate. and rake or fork in. fitted with a fine rose.

Soil and mixes 1

Plants growing under glass, whether in a con- tions and may contain good reserves of ROOT SYSTEMS Container-grown plants have their root
tainer or in a bed in a greenhouse or frame, nutrients. The bed must be well drained and, systems confined and therefore nutrients
have access to lower levels of soil nutrients unless it was previously part of a fertile Plants growing in open ground have room must be added to the soil available.
than do plants in open ground. Therefore soil garden, extra organic matter should be to expand their root system in order to
in beds needs to be enriched, and special added. Well-decayed manure, garden com- search out water and nutrients.
soils or mixes are required for pots or con- post, leal-mold, peat or other organics should Replacing soil
tainers. An understanding of the nutrients be dug at a rate of one 2 gallon bucketful per
necessary to plant growth is important in square yard, ideally some weeks before plant-
order to judge what needs to be added to ing. Spread balanced fertilizer over the bed
basic soils and growing mixes to ensure just before planting. Apply at a rate of 3-4 oz
health (see page 45). per square yard. If the top-soil was stripped
from the area prior to the erection of the
Beds provide a larger root run than do greenhouse, the existing sub-soil should be
containers, and therefore need less enrich- removed from the border site to at least one
ment. But the soil in the bed must be in good spade depth. Replace it with good top-soil or
condition and well drained and aerated. Also, a mixture of loam and one of the organic
soils in beds may become infested with build- matter sources mentioned above.
ups of pests and diseases, especially if the
same crop is grown year after year. Con- Mixes
sequently the soil must be changed, or Apart from natural soil beds, plants can be
sterilized, regularly if beds are used. grown in special mixes or composts, or in
inert media to which are added nutrients in
Beds fluid form (see Hydroponics, page 49). The
Ground level beds or borders created from root systems of plants growing in containers
the soil on which the greenhouse is placed are confined to a very much smaller volume
can provide the best possible rooting condi-

Greenhouse beds

1 Improve a greenhouse or frame bed by 2 Just before planting, rake in a balanced 1 If good top-soil is lacking, remove 2 Add good top-soil or a mixture of loam
digging in organics such as well decayed fertilizer at a rate of 3-4 oz per square yard. exposed sub-soil to at least one spade's and organics to bring the bed back to the
manure or garden compost at a rate of depth. Deal with any drainage problems. original level. At intervals add organics and
2 gallons per square yard. general fertilizer to maintain soil fertility.

Soil and mixes 2

of soil than they would normally occupy in a to grow a wide variety of plants well, soon STERILIZATION 1 Pass good-quality, dry, fibrous loam
bed or border (see box). If ordinary garden became popular, and is still widely used. through a 1/2 in mesh sieve. Prepare sieved
soil is used in containers, vigorous plants in Commercially, loam is pasteurized in loam to form a 6 in layer in the steamer.
particular rapidly use up the available Any good potting medium must be well specially constructed flat-bottomed bins
nutrients. This can be corrected by the aerated and free-draining, but moisture- or troughs injected with steam from
application of extra minerals in the form of retentive. It must contain sufficient fertilizers below. There are also electric sterilizers,
solid or liquid fertilizers, but plants will be to supply all the needs of the plants for as long small versions of which can be bought and
more successful if they can be kept growing as possible. In addition, it should be free from used by amateurs who garden on a
at a steady rate from the beginning. To this weed seeds, pests and disease organisms. moderate scale. Small quantities of soil
end it is necessary to create a richer, well- These can be present in the basic loam which can be pasteurized in the kitchen, using a
balanced soil for container-grown plants. is an ingredient of most mixes. The John steamer saucepan. Pass the loam, which
Compost formulae In the past, professional Innes formula demands that the loam be should be almost dry, through a1/2 in mesh
gardeners devised their own formulae for sterilized to destroy harmful organisms. Al- sieve and place a 6 in layer in the steamer.
container soil, using in varying proportions though the term "sterilized" is widely used Bring 2 in of water to the boil in the sauce-
such basic ingredients as turfy loam, decayed in connection with soil and mixes, the loam pan. Then put the lid on the steamer and
manure and leaf-mold, plus various ferti- is actually heat-pasteurized, because it is allow the loam to heat up. A thermometer
lizers. These potting media were known as not desirable to kill all life in the soil. must be used throughout the operation (a
composts, not to be confused with the de- Loam The key ingredient of the John Innes candy thermometer is suitable) and once
cayed vegetable matter known as garden formula is loam, the subtly-blended soil com- the surface of the loam reaches 82°C/
compost. The American term mix or potting posed of clay, fine sand, humus and minerals 180°F it must be kept as steady as possible
mix is now commonly used. The need for a that is found under long-established valley for 10 minutes. As soon as the 10 minutes
reliable standardized mix became imperative pastures. To create the finest loam the top are up the loam must be turned out to cool.
for research purposes as horticulture de- 4 - 6 in layer of pasture turf is removed and
veloped. In the 1930s the John Innes Institute stacked in layers. Between each 10 in layer of Loam can be steamed in large amounts
in England devised such a formula. It proved turf a 2 in layer of strawy manure is laid. The by passing steam from a boiler into a pile
stack should not exceed 6 ft high and wide of soil covered with a tarpaulin.

Making loam

1 Cut sods 4 - 6 in deep from good pasture. 2 Water the stack, which should be no 2 Place the loam in the steamer and bring Alternatively, use a purpose-made soil
Stack them grass side down in a sheltered more than 6 ft high and wide, and cover the water in the lower portion to the boil. sterilizer, which heats water by means of
position, adding a 2 in layer of strawy well with heavy-duty plastic sheeting. Leave Keep at 82°C/180°F for 10 minutes. an electric element.
manure between each 10 in of sod. tor six months until the sods have rotted.

Soil and mixes 3

and the sods must be moist or made so as Preparing mixes 2 Fill the box with the first of the ingredients 3 Spread the first of the ingredients on a
the work proceeds. Ideally, the stack should to the 10 in level. Do not compact the hard, dry surface.
be made in an open shed to protect it from 1 Prepare a bushel box for measuring ingredients.
the rain. Alternatively, cover the top with ingredients. The box should measure 22 in
heavy duty plastic sheeting. The stacked by 10 in. Mark the 10 in depth on the inside. 5 Add further ingredients in layers, 6 When all the ingredients have been
sods will turn into high quality loam in about sprinkling lime and fertilizers between added, mix the resulting heap with a clean
six months. Suitable pasture turf is in short 4 Sprinkle lime and fertilizer, according to each layer. shovel until the mix is an even color.
supply and some of the commercial potting the formula being followed, onto the pile.
mixes sold are made with inferior loam.
Generally speaking, however, such com-
posts are still superior to garden soil and
equal to other substitutes. Test a mix
before purchase by handling a sample. A
mix made with good loam will have a high
fiber content.

How to make soil mixes The first stage in
making soil mixes to one of the John Innes
formulae is to sterilize the loam (see page 43).
The mix should be made up as soon as the
loam cools. Ingredients must be mixed well
to obtain an even and uniform end product.
It is helpful to have a bushel or half-bushel
box in which to measure the ingredients, as
lime and fertilizers are normally added at a
bushel rate. A bushel is the amount that will
fit into a box 22 in x 10 in x 10 in without
compacting. Evenly layer the ingredients into
a pile on a clean concrete floor. Sprinkle some
of the lime and fertilizers onto each sand
layer. When the heap is complete it will
clearly show layers of the various ingredients
as they are of varying colors. The whole
should be well mixed with a clean shovel.
John Innes formulae The basic potting mix
formula is: 7 parts by bulk loam, 3 parts
of coarse washed sand, and 2 parts of moist
moss peat. To each bushel of this mixture add
4 o z of John Innes base fertilizer and | o z of
ground limestone. This is a No. 1 compost
or mix. For a No. 2 mix add twice as much
fertilizer, and for No. 3, three times as much.
For lime-hating plants a neutral to acid loam
should be used if possible and the limestone
omitted.

John Innes base fertilizer is rarely available
commercially but can be made up as follows:
2 parts superphosphate, 2 parts blood meal
and 1 part sulfate of potash.

For the seed-sowing mix the proportions
are: 2 parts loam, 1 part peat and 1 part sand,
adding to each bushel 11/2oz of superphos-
phate and 3/4 oz of ground limestone, which

Soil and mixes 4

is omitted for lime-hating subjects. It is recom- mental work has been carried out to find become top-heavy. To overcome this factor PREPARING SOILLESS MIXES
mended that, except for very fine or slow alternative growing media. The most success- and to render dryish peat more readily wet-
germinating seeds, sowing is made direct ful substance of all has been peat, in both its table, it is an advantage to add a small Follow the bushel proportions listed on
into John Innes potting compost No. I, thus sedge and sphagnum moss forms. Soil mixes percentage of coarse washed sand. the left, with a quarter-bushel box (81/2 x
doing away with seed-sowing mixes. consisting purely of peat with mineral U.C. mixes A series of simple standardized 8 1/2 x 73/4 in) substituted if smaller quantities
nutrients added are now the most popular of peat and sand media has been devised at the are required. The necessary chemicals can
Although there is plenty of experimental all for the amateur market. Professional University of California. They are known as be applied one by one or in the form of
evidence to show the benefits of properly opinion, however, favors the adding of at U.C. mixes. There are three variations: 3 parts ready-mixed compounds available com-
sterilized loam, it must be clearly stated that least some loam to peat-based mixes. by bulk moss peat and 1 part sand; equal parts mercially. The nutrients can be added
good plants can be grown without it. Weeds, Peat mixes All-peat mixes have the advan- peat and sand and 3 parts sand to 1 of peat. as the mix is used to save prior mixing.
pests and diseases will occur and have to be tage of being comparatively sterile and of To this is added a special fertilizer. If a commercial compound is to be used,
dealt with, but everything else considered, being light and fairly clean to handle. They Soil mixes for special purposes Lime-hating ensure that it includes the necessary trace
the risks are not high. Weeds are a problem have proved remarkably successful for a wide plants such as azaleas must be grown in lime- elements as well as the basic nutrients.
when seed sowing and it is advisable to use range of container-grown plants providing free mixes. These can be bought, or normal Slow-release forms of potassium and
one of the non-loam mixes mentioned below. they are used to makers' instructions. They John Innes formulae can be used with nitrogen can be added to soilless mixes
A particularly annoying possible result of must not be firmed when potting in the way the lime omitted. The formula for John Innes to provide for plant needs for three
using non-sterilized loam is the introduction loam-based mixes are and watering must acid compost, intended for acid-loving plants, months or longer, removing the need for
of earthworms. Their tunneling activities can be done with care. If the plant's rootball is: 2 parts loam, 1 peat, 1 sand, with 1 1/2-oz feeding. Trace elements can also be
slow down plant growth and render the becomes too dry and shrinks away from the calcium superphosphate and 3/4 oz flowers of applied in fritted slow-release form. Fritted
mix so well drained that most of the water sides of the pot, subsequent watering is less sulfur added per bushel. To give a mix for trace elements are released over a period
applied runs straight through. Kill the worms effective even when wetting agents are used. plants which require sharp drainage, add of months. Mixes should be used as soon
by watering affected pots with solutions of As much for this reason as any other, all-peat gravel or grit to the mixture. Plants which as slow-release fertilizers have been added,
potassium permanganate. mixes are best used for quick-growing short- need large amounts of water may benefit or they will build up in the mix before
term plants which require regular watering. from the addition of charcoal, which helps plants are present, leading to levels pos-
Soilless mixes prevent souring of the saturated mix. Steri- sibly damaging to plants.
Sources of good loam have been in short A disadvantage of peat is the lack of lized leafmold can be used in mixes.
supply for many years and much experi- weight a peat rootball has. Tall plants soon

SOIL NUTRIENTS The functions of the various nutrient normally present in most plants. It is essen- up from the water by the plant's roots and
mineral elements are summarized here. tial to those enzymes involved in the trans- combines with carbon dioxide, absorbed
Balanced feeding is the key to successful Nitrogen Essential for the formation of pro- porting of phosphorus within the plant. from the atmosphere, to form a sugar
plant growth although plant groups vary teins which in turn make up protoplasm, Deficiency shows as severe chlorosis of the compound which is the plant's food.
widely in their requirements of each the life-stuff of plants, nitrogen encourages leaves. Iron In its mineral form iron enters into
nutrient. If a plant is to thrive, its soil must leafy growth and promotes rapid growth the making of chlorophyll and therefore is
contain both the major and minor mineral in the spring and summer. Insufficient nitro- Calcium A major element but required in vital to all green plants. Deficiency shows
elements. The macro or major nutrients gen results in a general suppression of very small amounts, calcium is important as yellow to whitish shoot tips which often
are nitrogen, phosphorus, potassium, growth. for the movement of carbohydrates in the turn brown and die back.
magnesium, calcium, sulfur, carbon, plant and aids in the entry of phosphorus, Manganese Manganese is a trace element
hydrogen and oxygen. Of these, nitrogen, Phosphorus Phosphorus is a constituent of nitrogen and sulfur with which it combines. needed for the functioning of various
phosphorus and potassium (abbreviated protoplasm which plays a part in photo- Deficiency is rare but can show as wilting of enzymes and cell chloroplasts. Deficiency
to N, P and K) are required in large quanti- synthesis, the complex process by which shoots, leaves and flower stalks. symptoms vary but usually show as
ties. In addition to these nine mineral plants use light energy to make their own Sulfur Sulfur takes part in the formation chlorosis.
elements, plants also need minute food. Deficiency shows as thin shoots and of protoplasm and proteins. Deficiency is very
amounts of the minor, or trace elements narrow leaves. rare in well-prepared soil mixes but when Boron Deficiency of boron, a trace ele-
such as iron, manganese, boron, molyb- it occurs symptoms are similar to those of ment mainly concerned with cell division,
denum, zinc and copper. Potassium (Potash) Essential to the function- nitrogen. results in a crippling or death of developing
ing of enzymes active in the formation of tissues.
All balanced fertilizers contain nitrogen, fibrous tissue, sugars and starches, potassium Carbon, hydrogen and oxygen These ele- Molybdenum, copper and zinc All three
phosphorus and potassium with some makes plants more disease-resistant. De- ments are available from water and the are vitally important, in small quantities,
of the trace elements occurring as im- ficiency shows as thin growth. atmosphere. Oxygen is absorbed from the to the proper growth of the plant. They
purities. Some balanced fertilizers are Magnesium Magnesium is a constituent of atmosphere and helps to convert the plant's are often present in soil mixes.
compounded so as to include balanced chlorophyll, the important green matter food (sugar) into energy. Hydrogen is taken
amounts of trace elements.

Growing systems 1

Greenhouse growing systems are basec tainers allows staging and high-level shelves lesser extent cucumbers and tomatoes, are STERILIZING BORDER SOIL
either on open beds or some form of con- to be installed to maximize the use of growing traditionally grown on ridges or mounds of
tainer to restrict root run. The size, type and space, though the space below the staging is soil on benches. This system not only gives Empty the greenhouse and open ventila-
site of the greenhouse and the choice of to a large extent wasted. The decision must the plants more light than ground-level beds, tors. Then, wearing gloves, apply a for-
plants to be grown will dictate the kind of depend upon the crops chosen. but also enables the rooting medium to be maldehyde solution (one part of 38-40
growing system used. Another factor is the maintained at a beneficially higher tempera- per cent formalin to 49 parts water) at
manner in which the greenhouse is to be run. Open beds ture than is possible at ground level without 5 gal per square yard. Leave for 4 weeks.
Container, or restricted, systems lend them- If the greenhouse is sited upon good soil, and soil heating cables. This is because air can
selves more readily to automated watering that soil is free of pests, diseases and per- circulate below the bench as well as above
than do soil beds, for instance. If mist units or ennial weeds, open beds are the simplest the soil surface.
soil-heating cables are to be installed, then growing system. Open beds must contain a
a bench or staging system with containers or good-quality soil or mix. If the soil is in- Although open soil beds are the most
raised soil beds will be needed. adequate, modify or replace it (see page 42). If suitable growing system for such early crops
the site is wet and difficult to drain, a raised as lettuce, they are not economic of room
Containers are the best growing system if bed is the best solution. Construct one 9-12 in where ornamentals are concerned. Climbers
a large number of different plants is to be deep with the sides retained by boards or a and shrubs given a free root run make strong
grown in a greenhouse, for they can be brick or concrete wall. Fill the space above growth, but often at the expense of blooms.
moved and re-sited as the plants grow, thus the cultivated garden soil with good-quality
freeing space for further propagation and top-soil up to the level of the top of the wall. A further disadvantage of soil-level beds,
plant raising. Soil beds, on the other hand, do Beds may also be formed on stagings, but the particularly if tomatoes are to be the main
very well if only one major crop is to be grown stagings must be specially built to support the crop, is the possible build-up of soil-borne
at any one time. If, for instance, tomatoes or weight. Bench beds have the advantage of pests and diseases. This is inevitable if the
carnations grown for cut flowers are to be the bringing small plants nearer to the light and same crop is grown year after year. The only
main crop, then soil beds are preferable. Soil- to a level which makes cultivation easier. remedy is replacement or sterilization of the
level beds do not make use of the vertical They are especially applicable to the growing soil. Removing all the affected soil to 1ft
dimension of the greenhouse except when of alpines (see page 88). Melons, and to a depth and replacing it with fresh, or sterilizing
tall crops are being grown. The use of con- it (see page 43), is a laborious task. There are
Bench bed methods of sterilizing the soil in situ with
Raised bed
Ring culture

On wet sites, raise the soil by building a Beds can be placed on benches at waist Ring culture consists of a bed of aggregate, containing soil. Roots penetrate into the
9-12 in deep raised bed. Use boards, a level. The benches must have extra-strong placed in a trough or a plastic-lined trench, inert aggregate, where they absorb moisture
brick wall or concrete as sides. supports and drainage must be adequate. with plants grown in bottomless pots or rings and nutrients.

Growing systems 2

steam or chemicals, but in the main they are in open soil without restricting the plants' feeding has to be begun early in the plant's as it is easy to over-water a large volume of
not convenient for the amateur. The easiest roots to the confines of a pot. Each plant is growth. Proprietary liquid fertilizer, or a mix- all peat mix. The mix also dries out quickly
technique is to soak the soil with formalde- grown in a bottomless pot stood on a bed, ture consisting of 2 parts nitrate of potash, and it can be hard to re-wet. Feeding is
hyde (see page 46). The greenhouse must be or substrate, of gravel about 6-9 in deep. 3 parts sulfate of ammonia and 5 parts necessary to supplement nutrients.
empty when this is done, and the soil cannot The substrate is laid in a trough lined with super-phosphate (all by weight) should be
be used for at least one month after treat- plastic sheeting to prevent it coming into applied to each ring weekly. Apply at the This method can be used for a wide range
ment. Formalin will give fair control of fungal contact with the soil. Thus the roots are able rate of 1 oz of the mixture to 1 gal of water. of plants but is particularly useful for toma-
diseases but has no effect on eelworms. to pass out of the bottomless pot and enter The main disadvantage of the ring culture toes, peppers and small squash. It keeps plant
Cresylic acid, D-D and methyl bromide are the substrate. Water is applied to the sub- method is the need for precision in the roots away from the possible contamination
used commercially against eelworms, the strate only, not to the pots, as soon as roots application of water and fertilizer. Water of diseased soil in greenhouse beds. Growing
latter controlling fungi also, but these chemi- begin to penetrate the substrate. Dig out a loss can be high, especially early on when the bags can also be used in concrete-floored
cals should never be used by amateurs. The trench in the border soil at least 6 in deep and roots have not yet penetrated the substrate. greenhouses as temporary beds, and smaller,
work can be done by skilled contractors, but 16 in wide. Line the base and sides of the Ring culture means devoting the whole lighter growing bags can be placed on the
it is costly and only worthwhile on a large trench with heavy gauge plastic sheeting and greenhouse, or a large part of it, to tomatoes. staging. Supporting tall plants such as toma-
scale where other growing systems cannot fill it with the substrate. For the substrate Pot plants such as chrysanthemums can be toes is not very easy. The traditional cane
be used. a mixture of three parts gravel to one of ver- stood on the substrate later in the year. stake cannot be used, for it will not sup-
miculite is recommended. Other suitable Plastic growing bags Crowing bags provide port itself in the growing bag. It is necessary to
Restricted growing systems substrata are formed from perlite, stone restricted root runs but a larger than average fix strings or wires to the greenhouse frame
This term is used to describe growing systems chips or coarse sand. The substrate must be amount of growing medium. They are plastic above the plants and to train the plants.
where the plants' roots are in some way chemically inert. sacks usually the size of pillows, filled with
restricted by a container. an all-peat growing medium. They are laid The advantages of growing bags are free-
Ring culture The ring culture system was de- Place fiber rings or bottomless pots at least flat in the growing position and sections of dom from disease, a growing medium that
vised for, and is mainly used for, growing 8 in deep on the substrate and fill them with a the top cut away so that plants can be in- warms up fast, and convenience. Against
tomatoes (see illustration, page 46). The aim sterilized rooting medium such as John Innes serted. Drainage is provided if necessary by these advantages must be set the difficulties
of the ring culture system is to eliminate the potting compost No. 2 or 3. Soil-less media making slits along the edges near ground of accurately assessing feeding and watering
problems of the build-up of pests and diseases can also be used. Because of the small amount level. Watering must be carried out with care needs, and the possible build-up of mineral
of growing medium contained with the ring, salts in the peat. Crowing bags can also only
Growing bags be used once.

1 Place the bag on a flat surface in the 2 Add water to wet the peat-based 3 Water and feed the growing plants with needed. Feeding will be necessary as the
growing position. Slit the top to provide growing medium. care, for it is easy to over-wet the peat in plants grow, although the peat in the bags
planting spaces. the bag. Make drainage slits in the sides if has some nutrients added to it.

Growing systems 3

Straw bales The growing of plants under glass sium nitrate and 3oz of ferrous sulfate, all The straw bale system placed on fermenting wheat straw bales,
on slowly decomposing bales of wheat straw rates per bale. Water the nutrients in. The into which the roots penetrate. Do not use
can be considered a modern development of second method is that favored by com- The straw bale system is used for toma- straw sprayed with hormone weedkiller.
the old hot bed system. The reason for its mercial growers of tomatoes. toes, cucumbers and other food crops.
development, however, is quite different. Its Fermentation Whichever regime is applied, Plants are grown in ridges of soil mix. 3 Sprinkle soil or mix in a ridge along the
aim is that of ring culture, to provide a disease- the straw will heat up through fermentaion tops of the bales and plant. The roots will
free root run, primarily for tomatoes and and should reach 43o-54°C/110o-130°F. 2 Check the temperature every few days enter the straw.
cucumbers. It is thus a restricted system, Check the temperature with a soil thermo- during fermentation. Plant when it drops
although containers are not used. The straw meter every few days. When it drops to to 38°C/100°F.
bales are thoroughly wetted and fermentation about 38°C/100°F and is still falling, planting
is triggered by applying nitrogen, thus build- can take place.
ing up heat and giving off carbon dioxide.
Both are beneficial to the young plants, which To plant, pile a ridge of John Innes No. 3
are placed in soil mounds on the bales as the compost or equivalent mix along the top of
temperature in the bales starts to fall. The the bales and set the plants into this. Sub-
temperature in the center of the bale will, sequent watering and liquid feeding must be
under the right conditions, reach at least carried out regularly and thoroughly as the
43°C/110°F. Due to the difficulty in obtaining bales are very free-draining. Plants should be
straw and the relatively intensive care needed, supported with strings tied to the greenhouse
the system is a difficult one for the amateur. It roof (see page 50). Do not make the strings
also restricts the use of the greenhouse as too tight as the bales will settle.
the ammonia given off during fermentation
can damage some plants. Straw bale culture has the advantage of
Preparation Wheat straw bales are usually providing heat and carbon dioxide which aid
used as they do not decompose quickly; plant establishment, but bales take up a lot
barley and oat straw are inferior substitutes. of greenhouse space. Care must be taken not
Bales of 4 0 - 6 0 lb weight should be used. If to use straw sprayed with hormone weedkiller.
possible, they should be bound with wire Preparing the bales
rather than string, which can rot. They are
put on polyethylene sheet end to end in rows 1 Add fertilizers as listed in the text to the
where the plants are to be grown. The bales tops of the wet bales. Water the fertilizers
can be placed in a shallow trough lined with in.
polyethylene, which helps to save water
which runs through the bale. The ventilators
should be kept closed, and the greenhouse
temperature should ideally be around 10°C/
50°F to promote fermentation.

There are two alternative methods, one
fast, one slow. Choose that which fits the
period during which the greenhouse is free of
other crops. The slower method first involves
thoroughly watering the bales. Then water in
1 1/2 lb nitro-chalk (ammonium nitrate-lime mix-
ture) per bale. Four days later, apply a further
1lb of nitro-chalk, again watering in. Four
days after that, add 3/4 lb of a general fertilizer
and water in. Keep the bales damp at all
times. This method takes about 18 days.

The second method takes 7-10 days.
Thoroughly wet the bales and then apply 1 lb
of nitro-chalk, 6oz of triple superphosphate,
6oz of magnesium sulfate, 12 oz of potas-

Growing systems 4

HYDROPONICS Nutrient film technique to the gardener. However, some details of Hydroponics systems
Hydroponics is the technique of growing The nutrient film technique is a system of them are given so that the basic technique
plants in water and dissolved mineral nutrients growing plants in troughs of shallow re- may be understood. The pure solution system uses tanks of
without soil or other solid rooting medium. circulating nutrient solution. Polyethylene Pure solution This method uses nutrients solution, with plant stems supported by
I he fluid used has to contain all the nutrients troughs or pre-formed open gullies are laid contained in tanks about 8 in deep with fine horizontal wire mesh.
necessary to plant growth, and some kind of on flat surfaces in the greenhouse to a slope wire mesh stretched across the top to hold
support system is necessary to replace the of not less than 1 in 100. A narrow strip of the stems of the plants upright. The nutrient The flooded substrate system uses troughs
anchoring action of roots in soil. non-toxic capillary matting is laid along the solution needs to be artificially aerated and filled with an inert aggregate which supports
base of the gully beneath each plant con- regularly tested for pH, and must be changed the roots.
The use of a hydroponic system does take tainer. This ensures that no plant dries out in every two weeks. Among the disadvantages
away the skilled chore of watering and virtu- the early stages of growth and it leaves most of the pure solution method are the difficulty The drainage tank system is similar to the
ally eliminates diseases and pests of the root of the roots uncovered allowing good, in- of supporting plants adequately, and the fact above. A trench lined with perforated
system. However, for success regular chemi- expensive aeration. The nutrient solution, that only a limited range of species will plastic sheet is used.
cal analysis of the nutrient is essential. There containing a complete range of plant foods, tolerate the permanent immersion of roots.
are several nutrient formulae which the and if possible warmed to 25°C/77°F, is con- Flooded substrate Similar tanks to those used
amateur can try, some being available pre- tinually circulated by a submersible pump for the pure solution method are required for
mixed. If mixing is necessary, great care must through the troughs to a catchment tank at this system, but they must be protected with
be taken. An excess or a deficiency of any a flow rate of about 31/2 pints per minute per a layer of bituminous paint. Plastic-lined tanks
one or more minerals could spell disaster to gully. The systems available in kit form for or troughs are an alternative. The tank or
the plants. None of the commercial systems amateurs are based upon modifications of trough is filled with an inert aggregate, ideally
now available can be recommended to this technique. washed gravel or grit, though coarse vermi-
amateurs except to those interested in ex- culite, perlite, polystyrene chips, lignite or
perimenting for its own sake. Experiments Other hydroponics systems weathered coal ash may also be used. This
continue and a system wholly suitable for The other systems developed for commercial substrate is regularly flooded with the nutrient
amateurs may be developed. Meanwhile, kit horticulture are of mostly academic interest solution, the surplus being recycled. The
systems may interest enthusiasts. solution must be tested regularly for con-
matting and are covered by "tents" of centration and pH, and adjustments or
Nutrient film technique black polyethylene to reduce evaporation. replacement made when necessary. Replace-
Amateur systems are smaller. ment of the solution is more costly than
The warmed nutrient solution is pumped adjustment, but is more reliable, as the
from a storage tank along gently sloping correct concentration is assured. The flood-
gullies. The gullies contain a strip of capillary ing and draining operation ensures that
sufficient air gets to the roots and the sub-
strate gives the plants adequate support.
Drainage tank The drainage tank system is
a simplified version of the flooded substrate
method. The system can be adapted to a
variety of situations. Dig a trench and line it
as described under Ring Culture (page 46).
Make drainage holes in the sides about 3 in
above the base. Alternatively, any tank of
similar depth and width with the same pat-
tern of drainage holes can be used. Ideally,
use an absorbent substrate, such as vermi-
culite, perlite or lignite, the last being recom-
mended. Washed sand that is not too coarse
and thus has good capillarity is also suitable.
Add nutrient solution to the substrate regu-
larly, the surplus draining away, a reservoir
remaining below the drainage holes. Less
nutrient is needed than for other methods,
and checks are less frequent.

Plant supports

Many greenhouse plants require some kind cause for instance pots or growing bags are attached. Wires should be kept taut by the can be used in wooden-framed houses.
of support to control and direct their growth. being used, drop lengths of strong string from use of a straining bolt at one end of the wire. Supporting plants in growing bags It is not
Examples are tomatoes, fruit trees and orna- secure fixings in the greenhouse roof to the Fix wires for fruit trees 15-18 in apart. Crapes possible to drive supports into the growing
mental climbers. The plants that require sup- base of each plant. Attach the string loosely need wires at a 10 in spacing. bag, as the small amount of soil will not
port outdoors, such as certain shrubs and around the plant beneath the lowest true hold a stake or cane and the plants which
annuals, will also need support under glass, leaf. Twist the string gently around the plant Wires can be used vertically to support grow up it. Self-supporting metal frames can
though the supports need not be as strong as as it grows. Do not allow the string to become climbing crops such as beans and ornamental be obtained which stand over the bag.
those used in the open. Permanent systems too tight. climbers. In all cases, attach the plants to the Alternatively, drop strings from the green-
are needed for some plants such as grape Netting Plastic or plastic-covered wire net- wires with soft string as necessary. Some house framework to the plants or attach
vines. Such supports are attached to the ting can be draped from the greenhouse forms of plastic netting are perishable and plants to wall wires or nets.
framework of the greenhouse, by nails or structure along the line of the plants. Support rot after a season or two. Do not use such Supporting plants in pots Lightweight wire
screws in the case of wooden frames, or by top and ends of the net securely to the frame- netting for perennial plants. Rigid wire or frameworks can be bought which are inserted
clips or bolts to metal frames. Other crops work. Gently guide the plants through the plastic-covered wire netting can be fixed, into the potting mix. Several light canes
such as tomatoes require temporary props. netting as they grow, tying in with soft string using battens, to walls or greenhouse frames tied together in a fan-shape achieve the same
These are similar to those used outdoors, but as necessary. Netting of varying mesh sizes to provide support for climbing plants. result. Bushy twigs, as used outdoors for peas,
use is often made of the greenhouse frame- can be used. Some crops, such as melons and Fastenings Metal-framed greenhouses need are useful for supporting small climbers and
work to anchor them. cucumbers, require large-mesh nets. drilling, or the addition of special bolts, be- other ornamental plants. If flowering plants
Wires Fruit trees and climbers can be trained fore wire or other support systems are such as carnations are being grown for
Canes Bamboo or wooden canes can be up permanent or temporary systems of wires erected. Special bolts are available with T- cutting in large numbers, plastic or wire
used in borders where there is sufficient soil stretched horizontally along greenhouse shaped ends which slot into the glazing bars netting can be stretched horizontally above
to anchor them securely. Use one cane per walls. In lean-to greenhouses, screw eyes can of most aluminum greenhouses. To these the bed or staging and the plants allowed to
plant, of a height suitable for the mature be attached to rear walls and 14 gauge gal- bolts attach drilled brackets between which grow through it.
plants. Insert them on planting. Tie the plants vanized wire fixed between them. Alterna- the wires can be fixed. Wooden battens can
to the canes with soft garden string at 12 in tively, fix vertical battens to the wall and drill be attached to the bolts to provide easy Perennials Fruit trees and climbers need
intervals. them for bolts, to which the wires are permanent or temporary fixing points for robust support systems to control and direct
Strings Where canes are impracticable, be- strings, nets or wires. Ordinary screws or bolts their growth. Avoid perishable materials.
Netting
Canes Strings Tall crops Grape vines Lean-to walls

Tie the plants to bamboo Loosely tie strings below the Wire or string netting Tall or heavy crops need Vines require a rigid system Climbers can be trained up
canes at 6-12 in intervals, plant's first true leaf, wind attached to the greenhouse stronger strings or wires of horizontal wires at 10 in a framework of wire mesh
using soft garden string. them around the stems and frame can be used to and strong fixings to avoid spacings, firmly attached to fixed to battens.
then run them to the frame. support plants. collapse. the greenhouse frame.

Pots and potting 1

Until the advent of methods such as ring mainly because they did not have the porous Drainage All pots should have adequate 5 - 6 in. Pots are normally about as deep as
culture and growing bags, most greenhouse quality of clay. However, as clay pots become drainage holes in the base. Lack of drainage they are wide, but half pots—half as deep as
plants were grown in containers. There were more and more expensive, and often difficult leads to saturated soil and rotting roots. their width—are also used. They are often
primarily a range of plastic or clay flower pots, to obtain, the controversy fades into the Good drainage also allows capillary watering called alpine pots as one of their main uses is
with tubs being used for larger, semi- background. It has been widely proved that systems to be used efficiently. The drainage for alpines and other low-growing plants.
permanent plants. Containers are still the plastic pots will grow plants just as well as holes allow water to rise up into the soil Half pots can also be used for raising seed
main tool for propagation, and they find clay, and it had become clear that they have from the capillary medium below. Many and for other propagation work when only a
favor with gardeners who want to concen- certain advantages. The first advantage is that plastic pots have a raised rim around the small quantity of material is being raised. The
trate on ornamental greenhouse plants. They plastic pots are much cheaper than clay. They base. This lifts the drainage holes clear of the broader the base of the pot, the more stable
provide the most versatile way of growing a are also more durable and easier to clean, for bench or shelf on which the pot is standing, it will be when it contains a possibly top-
wide range of plants in a small greenhouse. they do not harbor dirt. Clay pots need allowing water to drain away through gaps heavy plant.
Pots come in a wide range of sizes, and tubs soaking, scrubbing and sterilizing between in the rim. Without such a rim, water can be
extend the size range upwards. There are also use, whereas plastic pots can be wiped clean prevented from draining away. Alternatives to pots
several types of disposable pot, including with water and detergent. Plastic pots are Size and shape Pots are traditionally round,
those formed from organic material which also lighter than clay, which makes for easier and round pots have advantages in display- The illustration below left shows the range of
can be planted with the plant. handling. However, because they are lighter, ing plants. They are also easier to fill with alternatives to the traditional pot that is avail-
plastic pots when used with light soilless soil, especially in the smaller sizes, than able. Clay pots (a) have been joined by plastic
Whatever container is used, there are mixes may be top-heavy. rectangular pots. Square pots do have the pots (b), also available as half pots (c). Shallow
certain principles which must be followed merit of being economical on space. More seed pans (d) are useful for sowing in small
when potting, re-potting and potting on Plants in plastic pots need watering less can be fitted onto a shelf or into a propagating amounts. Non-rigid pots such as black plastic
plants. These operations are covered in frequently than those in clay, because clay case. They contain a greater volume of soil sleeve containers (e) are often used for trans-
detail on pages 52-54. pots are porous. The difference is minimal than round pots of the same diameter. planting and for plants for sale. Disposable
Clay and plastic pots It was once asserted when plants are well rooted and growing pots include peat rectangles (f), individual
that only clay pots could be used to grow vigorously. Plants in plastic pots therefore Pots are measured by their diameter at the peat pots (g), paper pots (h), peat pellets (i)
plants successfully. Plastic pots, when first need less day-to-day care than those in clay, rim in inches. Two sizes should be acquired and soil blocks (j). Flats in w o o d and plastic
introduced, were viewed with suspicion, but there is a danger of overwatering. as the basis of a stock of pots: 2-21/2 in and complete the range (k and I).

CONTAINERS Potting bench Soil blocking

A potting table or bench with sides and a Moisten special peat-based blocking
back keeps soil mix away from growing mix and press the blocking machine into
areas. it. Use the blocks 24 hours later.

Pots and potting 2

Disposable pots Peat pots and soil blocks Peat pots can be the plunger a little to consolidate the soil even when filled with damp soil mix. Make
Several alternative systems have been de- bought individually or in strips and blocks. mix. Place the soil blocks on a flat so that sure also that the seed flats chosen are of
veloped to avoid the problems of root dis- While they have the advantages in cutting they are touching and leave for 24 hours to good quality plastic: some sorts become
turbance that result from growing in pots or the amount of root disturbance described consolidate. Then insert the seed or seedling. brittle when exposed to sunlight for any
flats. Seedlings grown in flats, for instance, above, they are relatively expensive. They Pot on or plant out when the roots begin to length of time.
are traditionally pricked out into small pots, are useful for sowing large seeds such as emerge from the sides of the block. Keep the
then moved again into individual pots or into beans. Soil blocks also involve expense, for a block moist at all times as the peat-based One advantage of wooden flats is that a
the open garden. Sowing in soil blocks or peat special machine must be bought. However, blocking mix is difficult to re-wet. side or end can be easily prized away to allow
pots makes these moves unnecessary. The the cost of the blocking machine can be set Substitutes for pots Plastic dairy produce seedlings to be slid out in a block. If wooden
block or pot is planted with the young plant, against the saving in pots, whether of plastic containers, paper or plastic cups and similar flats are used, they must be carefully (leaned
and provides it with extra humus as it is or peat, that soil blocks bring. Special soil substitutes can be used in place of pots when between use. Without careful maintenance
becoming established in its new pot or bed. mix is needed, but soil mix or its ingredients expense is a major consideration. Punch they rot easily and thus have a shorter lift'
Paper and papier mache pots have the same has to be purchased anyway, and its cost is adequate drainage holes in the base of the than plastic flats.
effect. Bedding plants are often raised from the only factor once the machine is paid for. pots, and use the correct mix, and good
seed commercially in strips of expanded results should be obtained. Substitute flats may be created by press-
polystyrene which contain holes for seed and The blocking machines produce either ing into service such things as fruit boxes,
soil mix. This material is heat-retentive and square or hexagonal blocks about 2 in high, Seed flats plastic and polystyrene cartons and kitchen
easily broken to release the plants on planting with a depression in the top for the seed to be Just as plastic pots have replaced clay ones, foil or plastic food containers. Cleanliness and
out. However, the strips can only be used sown or the seedling pricked on. To make a so wooden seed flats have been superseded good drainage are the main conditions; when
once. Plastic sleeve pots, also widely used batch of soil blocks, moisten some special by plastic. Flats are vital for raising larger they are achieved just about anything will do.
commercially, can be used for pricking on blocking mix in a bucket or bowl. Test numbers of seedlings. Many propagating There is, however, no substitute for the neat
seedlings which are later to be planted out. the moisture content by squeezing. If the cases are designed to take the standard-sized appearance of a bank of clean plastic or
When filling such non-rigid containers with mix crumbles a little, it is ready. If it falls seed flat, which measures 14in x 81/2in x 21/2in. wooden flats.
soil mix care must be taken to fill all the apart, it is too wet. If it does not start to Half-sized flats, 6 in x 81/2 x 21/2, are also used.
corners to avoid air pockets. crumble, it is too moist. Push the mould into Plastic flats must be well drained and rigid, Other equipment
the damp mix and when it is full depress A sieve with a 1/2 in mesh, a further fine sieve,
Potting and a supply of labels will be required.

Crock the pot to provide adequate drainage. Hold the plant in the pot by a leaf and pour Firm gently with the finger tips to avoid air Place the potted plants in a position w i t h
Moisten a supply of potting soil and water in compost with a circular motion. Tap the pockets around the roots of the plant. good light and water to settle the soil
the plants to be potted. pot to distribute the soil. around the roots.

Pots and potting 3

Potting procedure 2 ft deep. The sides and back can be 6-12 in the seedling and roots from the soil. Place surface and the pot rim to allow for efficient
Potting, re-potting and potting on are some high. The bench can be placed in the green- the plant in the pot and pour fresh soil watering. As a guide, aim at a space equal to
of the most frequent tasks the greenhouse house or in a shed or outhouse, wherever around the roots. Make sure that the plant is one-seventh or one-eighth of the depth of
gardener faces. While they are not difficult, there is space. If the bench is in the green- not potted too deeply—the base of the stem the pot. As much water as will fill this space
the basic techniques should be mastered, for house, be sure not to leave surplus soil should be level with the surface of the soil. should thoroughly wet all the soil with a
if plants are not potted properly, no amount lying on it or on the floor, where it will attract Distribute the soil around the roots with a little surplus trickling out at the bottom.
of subsequent care will make them grow to pest and disease organisms. circular motion of the hand or trowel. Tap
their full potential. Preparation Assemble the pots, drainage the pot gently on the bench to settle the soil Potting on
material such as crocks if needed, and the around the roots. Make sure that the plant W h e n the young plant has filled its container
Potting is the initial transfer of a seedling, soil mix. Carefully choose pots no larger is centered in the pot. If roots still show with roots it will need p o t t i n g on, that is,
rooted cutting or bought-in plant to a pot or than necessary: most plants grow and look after tapping, add more potting soil, then removing from its container and placing in a
other container. Potting on is its transfer to a better in small rather than large pots. Use firm lightly with the fingertips. A further tap larger one. First water the plant, but do not
larger pot as it grows. Re-potting is move- a soil mix suitable for the plant being grown, on the bench will level the soil leaving it soak it. Invert the pot onto an open hand
ment to a new pot of the same size as the old, and make sure that it is well mixed. Soil ready for watering. The degree of firming with the plant stem hanging down between
the prime object being to renew some of the should be damp but not wet. It should be can vary with the type of plant and soil the middle and index fingers. Gently rap the
soil mix around the rootball. possible to pour it cleanly into the pot by type. All-peat mixes require little firming, pot rim on a firm wood surface, or tap it with
The potting bench The first step is to have a hand or with a trowel. tapping followed by watering will settle the a light hammer, and lift the pot off. If this
proper work surface for potting. A bench or medium amongst the roots. Loam-based operation does not work the first time, the
table with a back and sides allows the soil Potting mixes, particularly when used for vigorous plant may be too dry and watering should be
mix to be piled up. If there are never more Seedlings or cuttings growing in flats or pots plants, can be made firm with light finger repeated before trying again. Prepare a new
than a few plants to pot at a time, construct a should be watered. Loosen them from their pressure. The former practice of ramming pot which should be large enough to allow
portable bench from a 2 ft square board with container by knocking the sides. Remove soil firm with a potting stick is now con- about an inch gap all round the rootball to
a retaining rim 3 - 4 in high around three sides. seedlings carefully, holding them by the seed sidered unnecessary. the right level, then fill the gap with fresh soil,
This board can be rested on the greenhouse leaves, not the stem. Keep the rootball as tapping and firming as described above.
bench when required. A permanent potting large as possible. Use a dibble to help free When the potting operation is completed Water to settle the soil.
bench should be at waist height, 3 ft wide and there must be a space between the soil

Potting on PEAT PELLETS

Water the plant. Select a pot 1 in larger than Hold the plant stem between the fingers Place the rootball in the new pot and Peat blocks and pellets allow seedlings to
the present pot and crock it if necessary. and invert the pot, tapping gently so that sprinkle moist soil around it. Firm grow and be transplanted without root
the rootball slides out. carefully. disturbance. The plants should be potted
or planted out when the roots emerge
from the block. The netting will decom-
pose in the soil.