Crops in the British Isles can be summarized as follows:
- top (tree) fruit; which in turn can be sub-divided into pip fruit,
mainly apples and pears, and stone fruit (plums, cherries and
- soft fruit which in turn can be sub-divided into bush fruit (black,
white and red currants; gooseberries, blueberries), cane fruit (raspberries, blackberries, loganberries and other hybrids;)
There are many differences between vegetable and fruit growing,
most of which are related to how long the crop is in the ground before
replanting. Whereas most vegetables are in the soil for less than a year,
fruit is in for much longer; typically strawberries last for two to three
years, raspberries for eight to ten years and top fruit for some 15 to
20 years or more. Fruit plants should not be replanted in the same place.
The particular site
requirements are as follows:
- freedom from frost is a major consideration as most fruit
species are vulnerable to low temperatures which damage blossom
and reduce pollination. Cold can also damage young tender
growth which leads to less effi cient leaves and russeting of
- deep, well-drained loams are ideal for most types of fruit growing.
Unlike vegetable production, heavier soils are acceptable because the
soil is not cultivated on a regular basis.
- soil pH should be adjusted before these long-term crops are
established; most benefi t from slightly acid soils, but
allowance should be made for the normal drop in pH over time (see
p358). Blueberries and other Ericaceous fruits are the exception,
requiring a pH of 4.5 to 5.5.
There are many production methods and the choice is mainly related to
the space available, aftercare (such as pest and disease control) and the
method of harvesting; taking fruits from large trees presents diffi culties
and making it easy for the public in 'pick your own' (PYO) situations is
essential. Several methods lend themselves to smaller gardens, growing
against walls or as hedges. These considerations greatly infl uence the
selection of cultivar and rootstocks.
|Figure 1.4 Fruit tree forms
Top fruit can be grown in a natural or 'unrestricted' way in which case
the size of the tree depends on the cultivar and whether it is grown as
a standard, half standard or bush. Restricted forms include cordons,
espalier, fan and columns (see Figure 1.4). Rootstocks
play an important
part in determining the size of top fruit trees, e.g. by grafting a cultivar
with good fruiting qualities on to the roots of one with suitable dwarfi ng
characteristics. Excess vigour, which can lead to vegetative
growth (leafi ness) at the expense of fruit, may be reduced by restricting
nutrient and water uptake by growing in grass,
ringing the bark or, more rarely, root pruning. Soft and cane
fruits are usually grown on their own unrestricted roots.
Training and pruning
plays an important part of the husbandry of
fruit growing. The shape of trees and bushes is established in the early
years ('formative pruning'). Suitable frameworks and wiring systems
are set up for many of the growing systems (see Figure 1.4) and the
new growth has to be tied in at appropriate times. Pruning plays a major
part in maximizing fl owering and fruiting, as does the bending down of
branches. The shape created and maintained has a signifi cant
effect on pest and disease control; the aim is usually to have an open
centre which reduces humidity around the foliage and lets the
sunlight into the centre of the tree to give a good fruit colour. Pruning is
also undertaken to remove weak and diseased growth.
of flowers is required before fruits are formed. In
order for this to be successful pollination
needs to take place.
Most top fruit is not self fertile. Therefore, another plant is needed
to supply pollen and insects are required to carry it. Since successful
pollination will only take place when both plants are in flower the choice
of cultivars becomes limited; later flowering cultivars do not pollinate
early flowering ones. Apple cultivars are placed in seven groups to
help make this choice whereby selection is made from the same group
(ideally) or an adjoining one. However, choice is further limited because
some cultivars are incompatible with each other. In particular,
triploid cultivars, such as Bramley’s Seedling, are unable to pollinate
any other. Similar considerations apply to pears, but some
plums, cherries and peaches are self fertile.
of top fruit is by grafting, raspberries by
suckers, blackberries by tip layering and strawberries by
Pest and disease
control methods described later. Note that Certification Schemes
and Plant Passports
are particularly important
for plants that are propagated by vegetative means where viruses can be
a signifi cant problem. This is especially the case where they are grown
for many years before renewal.
fruit for immediate sale or consumption must be undertaken
at maturity to present the full flavour of the variety. Techniques involved
in handling fruit to prevent bruising and subsequent rotting require an
understanding of fruit physiology. Stone fruits, e.g. plums and cherries,
are picked directly into the market container being graded at the same
time because these fruits often have a very attractive bloom which
is lost if handled too often. Soft fruits will not tolerate washing or
excessive handling and grading is done at picking. With strawberries
the stalk is not left attached, only the calyx, to prevent it sticking into
an adjoining fruit and causing a rot. Machine harvesting of raspberries
for the processing industry is less important now as most fruit is
grown for the dessert market and is often protected during harvest by
temporary, polythene covered structures known as 'Spanish Tunnels'
or 'Rain Sheds'.
of fruit crops requires considerable skill and technique. Pip
fruits, e.g. apples and pears, must be at an exact stage of maturity for
satisfactory storage. If storage is to be for a long time, e.g. the following
spring, then controlled atmosphere storage is used, where the levels of
are controlled as well as temperature and humidity.
Soft fruit crops are harvested during the summer when the ambient air
temperature is high and the fruit will continue to ripen after it has been
picked. It is therefore essential to lower the temperature of the fruit
quickly, known as removing 'field heat'. Refrigerated storage is used,
but excessively low temperatures will cause the fruit to respire even
more quickly when removed from store. This causes punnets
(fruit containers) to mist up and the fruit to rot more quickly. The
maintenance of the fruit at a cool temperature from grower to consumer
is referred to as 'cool chain marketing'.
Protection for plants can be in the form of simple coverings such as
fl oating mulches, cloches or cold frames and more complex structures
such as polytunnels or glasshouses.
The advantage of protection by these various methods is that to a greater
or lesser extent they modify weather
conditions, particularly wind, and
so keep the environment around the plants warmer. This factor enables
plants to be grown over a longer season, which is advantageous where
continuity of supply, or earlier or later produce commands a premium.
In leisure horticulture, the protection offered enables a wider range of
plants to be kept, propagated and displayed.
The changed environment in protected cropping necessitates a careful
management approach to watering and ventilation. Any plants
requiring insect pollination have to be catered for. Pests, diseases
and weeds can also benefit from the warmer conditions and tropical
species assume more importance.
, or conservatories, enable tender plants to be
grown all year round, especially if a source of heat
is also available.
Half hardy plants can be 'brought on'earlier and similarly plants can
be grown from seed and planted out when conditions are suitable after a
period of 'hardening off'.
The closed environment makes it possible to maximize crop growth by
using supplementary lighting, shade, and raising carbon dioxide levels.
Day length can be modifi ed by the use of night lighting and blackouts
to encourage flowering out of season. A wider range of
biological control is possible within an enclosed zone.
Greenhouses also allow work to continue even when the weather is
There are many designs of greenhouses, some of which are illustrated
in Figure 1.5. Others are much more ornamental rather than purely
functional. They range from the grand, as seen in the Botanic Gardens,
to the modest in the smaller garden. Although the structures can be clear
glass to the ground, there are many situations where brick is used up to
bench level e.g. Alpine Houses. Many older 'vinery' style houses were
substantially underground to conserve heat.
|Figure 1.5 Glasshouses
used for glasshouses depend again on their
intended purpose, but most are either aluminium and steel construction
or wood (usually Western Red Cedar). Those which are for commercial
production tend to be made of aluminium and steel with an emphasis on
maximizing light by increasing the height of the gutter and
using larger panes of glass. Aluminium is lightweight and very suitable
as glazing bars for glasshouse roofs, it is also virtually maintenance free,
but does transmit heat away more than alternatives such as wood. Where
more attractive structures are preferred, wood is often chosen although such structures are less effi cient in light transmission and require more
|Figure 1.6 Geodesic biome domes at the Eden
are usually glass or plastic although there are many
types of plastic available. Glass has superior light transmission and heat
retention. Plastics tend to be cheaper but are less durable. They have
poorer light transmission when new and most deteriorate more rapidly
than glass. Polycarbonate is often used in garden centres where the
danger of glass overhead is considered to be too great in public areas.
The biodomes at the Eden Project in Cornwall are made up of hexagonal
panels made of thermoplastic ETFE cushions (see Figure 1.6).
of the glasshouse depends on the intended purpose. For
many commercial glasshouses the need for winter light is the most signifi cant consideration, this is achieved with an east–west orientation.
However, the most even light distribution occurs when the house
is orientated north–south which may also be the choice if several
houses are in a block. For many decorative structures the orientation is
subservient to other considerations.
should ensure an open position to maximize light, but with
shelter from wind. Frost pockets need to be avoided and there
should be good access which meets the needs of the intended use. Water
is needed for irrigation and normally an electricity supply needs to be
availability is emphasized in the selection of structure, cladding and
siting, as this is fundamental to the growth of plants (see photosynthesis). Supplementary lighting
in the greenhouse is advantageous in
order to add to incoming light when this is too low. More
rarely, total lighting
can be used when plants are grown with no natural
light such as in growth cabinets for experimental purposes. Low level
lighting to adjust day length is used to initiate flowering out of season,
e.g. year round chrysanthemums, poinsettia for the Christmas market
Careful water management
is essential in the glasshouse where plants
are excluded from rainfall. A suitable supply of water, free from toxins
and pathogens, is a major consideration especially with
increasing emphasis on water conservation. For many, water
is supplied by hoses or watering cans with spray controlled with the
use of a lance or rose. There are many systems which lend themselves
to reduced manual input, and on both small and large scale automatic
watering is preferred, using one or other of the following:
- overhead spraying
- low level spraying
- seep hose
- trickle or drip lines
- ebb and flow
- capillary matting or sand beds.
Water is not only used to supply plant needs directly, but also to help
cool greenhouses. 'Damping down' is the practice of hosing water
on to the floor, usually in the morning, so that the evaporation that
follows takes heat out of the air. This increases the humidity
in the environment which can advantageously create a good
environment for plant growth. On the other hand, if done at the wrong
time it can encourage some pests and diseases. Water can
also be used to apply nutrients through a dilutor, either as a one-off event
or at each watering occasion; this is known as 'fertigation' and enables
the grower to provide the exact nutritional requirement for the plant at
particular stages of its development.
can be supplied by a variety of methods including paraffin,
electricity, methane (mains gas), propane (bottled gas) and, less
commonly now, solid fuel. Some commercial growers are installing
biomass boilers and some are in a position to use waste heat from
other processes. Fuel costs and environmental considerations have put
increasing emphasis on reducing the need for heat (choice of plants, use of
thermal screens, etc.) and reducing heat losses with insulation
such as bubble wrap (with consequent reduction in light transmission).
is essential in order to help control temperature and
humidity. Air is effectively circulated by having hinged
panes set in the roof and the sides (these are often louvre panes). The
movement of air is often further enhanced by the use of fans.
is used to reduce the incoming radiation. Although
much emphasis is put on ensuring good light transmission, particularly
for winter production, the high radiation levels in summer can lead
to temperatures which are too high even with effi cient ventilation.
Traditionally, shading was achieved by applying a lime wash. This has
been superseded by modern materials which are easier to remove and
some even become less opaque when wet to maintain good light levels
when it is raining. Most modern production units have mechanized blinds
which can also help retain heat overnight. Many ornamental houses will
have attractive alternatives such as external shades in natural materials.
options in protected culture are very extensive, but the
choice depends on whether the plants are grown in soil, in containers on the
ground or in containers on benching. Border soils
have been used over the
years, but they have many disadvantages, especially with regard to pest and
disease problems and the expense of controlling this (see soil sterilization). A range of composts is available for those who choose to grow in
containers. However, a signifi cant proportion of commercial
glasshouse production uses one of the hydroponics systems.
Pest and disease control
has special considerations because the
improved conditions for plants can also lead to major pest and disease
outbreaks which develop quickly. If the atmosphere becomes wet, too
humid or too dry even more problems can be expected. Furthermore this
environment supports organisms not commonly found outdoors such as
two-spotted red spider mites. Besides a range of cultural and chemical methods, the enclosed space makes it possible to use a wider
range of biological controls than is possible outside.
|Figure 1.7 Glasshouse
to control temperature, ventilation and lighting have
developed over the years to reduce the manual input (and the unsociable
hours) required to manage conditions through the growing season.
Some of the most exciting developments have occurred as computerized
systems have been introduced to integrate the control of light,
temperature and humidity. In order to control the conditions indoors the
systems are usually linked to weather stations to provide the
required information about the current wind strength and direction, rain
and light levels (see Figure 1.7). The use of the computer has made it
possible for the whole environment of the glasshouse and the ancillary
equipment to be fully integrated and controlled to provide the optimum
growing conditions in the most effi cient manner. It has also enabled
more sophisticated growing regimes to be introduced.
provide a cheaper means of providing an enclosed
protected area. They are usually constructed of steel hoops set in the
ground and clad with polythene, but in some cases, such as for nursery
stock, a net cover is more appropriate (see Figure 1.8). They are not
usually considered to be attractive enough for consideration outside
commercial production although they are often seen in garden centres.
|Figure 1.8 Net tunnel
offer many of the features of a greenhouse, but there
are considerable drawbacks besides looks; they tend to have limited
ventilation and, despite use of ultra violet inhibitors, the cladding
is short lived (3–6 years). Nevertheless there have been steady
improvements in design and there are many hybrids available between
the basic polytunnel and the true traditional greenhouse, utilizing
polycarbonate either as double or triple glazing.
(with wire hoops 30 to 50 cm high) are commonly used to
protect rows of vegetables. These are put in place after sowing or planting;
access and ventilation is gained thereafter by pulling up the sides.
are mainly used to raise plants from seed and to harden
off plants from the greenhouse ready to be planted outdoors. The simple
'light' (a pane of glass or plastic in a frame) is hinged on the base of
wood or brick and propped up to provide ventilation and exposure to
outdoor temperatures. The degree to which plants are exposed to the
outdoor conditions is steadily increased as the time for planting out
approaches. A frameyard
is a collection of cold frames.
were originally glass cases put over individual plants for
protection (cloche comes from the name of the cover used in old clocks).
They are now more usually sheets of glass or plastic clipped together
over individual plants, or rows of them can cover a line of vegetables
(mostly superseded today by low tunnels in commercial production).
|Figure 1.9 Fleece; an example of a floating mulch
are lightweight coverings laid loosely over a row
or bed of plants (see Figure 1.9) and held in place by stones or earth
at intervals. They provide some protection against frost, speed up
germination and early growth and provide a barrier against some pests.
They take three main forms:
- fleece, which is a light, non-woven material (polypropylene fi bre)
permeable across its entire surface allowing light, air and water to
penetrate freely. Humidity can be a problem as the temperatures rise.
- perforated plastic film is a thin gauge plastic fi lm perforated with
holes which allow it to stretch as the plants grow. High humidity is
less of a problem because of the holes. Films are made with varying
concentration of holes which allow for the requirements of different
crops. The greater the number of holes the less the harvest date is
advanced but the longer the cover can stay on the plants.
- fine netting does not offer the same protection from the elements, but
does help keep off pest attacks.