Growing Crops under Cloches
Gardeners discovered many. Years ago that a plant could be forced into early growth by protecting it with a glass cover. Eventually, a Frenchman, whose name has not gone into the history books, evolved a practical and efficient shape for forcing individual plants. It was a bell-shaped glass dome and it became known as a cloche, meaning bell.
The name has persisted to the present day, although cloches are no longer bell-shaped and they now protect whole rows instead of individual plants. The final change from the original concept has come about in recent years when glass, because of its cost, has largely been replaced by rigid plastic or polythene.
Since most vegetables are grown in straight rows, a number of cloches set in a line, with the ends closed to exclude, are ideal for producing early crops and for protecting tender plants.
Generally, sowing and planting are possible about a fortnight earlier than in the open.
This early start, resulting in earlier harvesting, makes it possible for more than one crop to be grown on the same ground in a‘ season.
As an example of a cropping programme lettuces, sown in October, may be cut in April, to be followed by early-fruiting dwarf tomatoes. These in turn, may be succeeded by spring cabbages planted in the open. The cloches, meanwhile, are transferred to another part of the plot to restart the cycle.
This mobility enables a gardener to use a cropping technique whereby cloches are moved from one row to another as the season progresses.
Early carrots, for example, may be given a good start by being covered in March and April. They then go on to mature in the open and the cloches are moved in mid-May to enable newly planted tomatoes to become established. Three to four weeks later the cloches are again moved, this time to protect heat-loving plants, such as aubergines and peppers, for the rest of the summer or until they are too tall.
Growing under cloches
If possible, prepare the ground at least a month before sowing or planting to give the soil time to settle. Dig in well-rotted manure or compost at the rate of a bucketful to the yard run.
About a fortnight before sowing or planting, rake into the surface soil a dressing of general fertiliser at about 2 oz (50g) to the yard run. Mark a row with a line, leave this in position, and cover the row with the cloches to warm up the soil. Secure the end panels with two canes driven into the ground.
The cloches must be removed at sowing or planting time and the purpose of leaving the line is to centre the row where the plants will get most headroom.
After sowing or planting, scatter slug pellets and replace the cloches in exactly the same position as when the ground was being warmed.
Sow small seeds about 4in (5 mm) deeper than in the open because the surface dries during the warming-up period. Do not water until the seeds germinate. Water the soil after setting out young plants, however.
After that, cultivation is the same as for growing in the open. Although the surface soil may look dry, a few inches down it will have about the same moisture content as the uncovered soil alongside. Capillary attraction ensures that water reaches the plants’ roots.
Although any type of cloche provides artificially benign growing conditions, you may need to take action when there are sudden changes in the weather.
If spring days are unusually warm, open up some continuous cloches or slide back the polythene of a tunnel cloche, to allow air to circulate. Replace or close the cloches an hour before sunset.
If late spring frosts are forecast, cover tender plants, such as tomatoes, with four or five sheets of newspaper in the evening and remove them in the morning.
A week before moving cloches from one row to another, harden off, or acclimatise, the protected plants that are about to be left in the open. To do this, leave off some cloches during the day and replace them in the evening.
Fruit under cloches
Melons and strawberries are the only fruit grown under cloches, but the results are usually highly successful.
Cloches serve a dual purpose when covering strawberries. They make it unnecessary to net against bird attacks and, if put in position in November, will provide an earlier crop than outside, generally in May. Any type of cloches may be used.
CONSTRUCTING AND USING TUNNEL CLOCHES
The cheapest form of cloche is a `tunnel’ made from a series of galvanised hoops pressed firmly into the ground and covered with a sheet of light-gauge polythene. A second hoop holds the polythene in place.
Kits containing hoops and about 35 ft (10.5 m) of 150-gauge polythene are obtainable from garden shops and centres. The hoops will last for many years, but the polythene deteriorates in sunlight and needs to be replaced with new sheeting every year or two.
The tunnels can be put in place or moved from row to row in a matter of minutes.
There is no need to move the cloches to gain access for sowing or planting, or to provide ventilation. Simply slide back one side of the polythene cover.
1. Insert the supporting wire hoops 3 ft ( 1m) apart, using a garden line as a guide to ensure a straight row.
2. Knot one end of the cover to a peg inserted 2 ft ( 610 mm) beyond an end hoop. Draw the cover over the hoops.
3. Secure the other end of the cover. Tension the cover by clipping the outer hoops on to loops in the supporting hoops.