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Choosing frames & cloches
FRAMES
Cold frames are perhaps most widely used for relieving the pressure
on space in the greenhouse in spring, and for acclimatising plants
raised in the greenhouse to the colder temperatures outdoors.
With or without a greenhouse they are invaluable in summer for
growing vegetables, in winter for protecting slightly tender plants,
and throughout the year for the propagation and protection of
seedlings and cuttings.
Most cold frames follow the traditional
design of a low front and high back, with a sloping top (called
a ‘light’). The purpose of the slope is to catch as
much light as possible, and to discourage rain and snow from lying
on the top.
The most commonly used material for
ready-built or ready-to-assemble cold frames is aluminium alloy.
Frames that come as a kit can be easily assembled simply by bolting
the pieces together.
Aluminium alloy frames are often
glazed to the ground. These let in plenty of light, which is a
significant advantage for many crops, such as lettuces and seedlings,
and the sides can be insulated against excessive heat loss in
winter with pieces of expanded polystyrene.
A frame is not difficult to construct
from scratch. A brick framework offers particularly good insulation
while timber also offers reasonable insulation and is easier to
work with. You can also buy timber-sided frames, though they are
likely to be more expensive than the home-made variety.
Glass is the best glazing material,
but clear plastic is adequate.
CLOCHES
Cloches are usually used to warm up the soil for early sowing
of vegetables and to protect and advance them for early cropping.
Those with tall sides or removable tops can remain in position
around those crops that benefit from extra protection, such as
aubergines and peppers. To get the most from them, use cloches
to extend the season at the end of the year by protecting late
sowings of crops such as lettuces and for overwintering plants
such as parsley.
Choose a cloche type that suits the
purpose for which it is likely to be used. Some of the least expensive
ones are perfectly adequate for soil-warming and encouraging early
growth, but may have only limited use beyond that.
BARN
The extra height of most barn cloches, and the greater usable
height close to the edges, because of the almost vertical sides,
make the barn cloche the most useful and versatile design, although
they are more expensive than simpler designs such as tent cloches.
A removable top will make watering and weeding easier.
TENT
The simple inverted V shape of the tent cloche makes it an inexpensive
choice. The angle of the glazing where it meets the soil, and
the overall low clearance, make tent cloches most suited to soil-warming,
germinating seeds and for early protection of young crops until
they become too tall.
DOME
These short tunnel-like, one-piece cloches are easy to move around.
Although the height may be little more than some tent cloches,
the curved profile enables crops to be grown much closer to the
edge than in some other cloche types. They are likely to be more
expensive than tent cloches, however.
TUNNEL
Continuous tunnel cloches are generally used in the vegetable
plot, for advancing crops such as carrots and for general soil-warming
prior to sowing. They are also widely used to cover early strawberries,
to encourage an early crop and to protect the fruit from birds.
Both ventilation and access for weeding and harvesting is achieved
by ravelling up the sides.
The cloches are sold as kits, with
hoops to push into the ground, a length of plastic sheet and tensioning
wires to hold the sheet in place. The covering is only likely
to last for a couple of seasons, but is inexpensive to replace.
Always use heavy-duty plastic treated to resist the destructive
effects of UV light. The hoops and wires will last for many years.
Semi-rigid plastic tunnel cloches
are also available. These come in short lengths with the plastic
held in place in a wire frame. A series of cloches can be placed
end to end to make a longer tunnel. Use special end pieces to
prevent the cloche becoming a wind tunnel.
FLOATING CLOCHES
These do not look elegant, and are really only practical in the
vegetable plot, but they are very effective. Within limits, they
stretch or expand as the crop grows, so you can leave them over
carrots and even cabbages, to provide protection from pests, such
as butterflies and moths.
They consist of a sheet, usually
made from perforated plastic or horticultural fleece, weighted
or pegged down around the edge of the bed with special plastic
pegs. Some environmental meshes can be used in a similar way.
The sheet has to be removed for weeding, but water will penetrate
through the small holes.
There is some natural stretch that
allows space for the growing crop, and further growth can be accommodated
by loosening the edges of the sheet as it becomes necessary. Low-growing
crops can be protected until ready for harvesting, but the sheet
must be removed from taller crops once the early protection is
no longer needed.
Frost protection will not be as good
as with most other types of cloche, but a floating cloche will
help to warm the soil, will aid germination, and almost certainly
produce better yields than crops which are unprotected.
INDIVIDUAL CLOCHES
Small individual cloches are useful for putting over single plants
that require a little protection. Some are made from waxed paper,
others from plastic. Large plastic drinks bottles with the bottoms
cut off are excellent, but leave the top off for good ventilation.
POLYTUNNELS
Plastic tunnels, shaped over special curved frames, are widely
used commercially, where appearance is unimportant but cost is
crucial. If you have a large garden, however, it is worth considering
a polytunnel for an unobtrusive area.
Polytunnels are not usually heated,
so the main benefit is derived from wind and weather protection,
but the plants within them are almost always more advanced than
those in the open garden. Many bedding plants can be grown on
without additional heat, once the period for frosts has passed.
Although you can use staging in polytunnels,
crops are usually grown in the ground or in containers on a weed-suppressing
groundsheet.
The plastic covering will stay in
good condition for only a couple of seasons, but is relatively
inexpensive to replace.
Ventilation is often a problem, so
a door at each end that can be opened or rolled up is an advantage.
WATERING AND WEEDING
If the cloches are to be used just for short-term soil-warming
and early protection, the weeding can be done once the cloches
have been removed. If cloches are to remain in place for a long
period, however, choose a design that allows easy access, or one
where the whole cloche can be lifted and replaced without too
much effort.
Sideways penetration of water in
the soil will provide some moisture for the roots of established
plants but for rapid and full germination the soil must be kept
moist as well as warm. Many growing crops, such as carrots, also
require regular watering in dry weather. Some cloches are designed
to allow water to penetrate through small holes, and a few have
a built-in hose watering system, but for most you will have to
remove the cloches temporarily for watering, or run a seep hose
beneath the cloches.
Taken from Reader's Digest New Gardening Year - a month-by-month
guide to success in the garden.
Feature: Erica Miller, Homebase
Click
here to see a list of UK suppliers of frames
and cloches
