Conservatories, greenhouses, poly-tunnels, and cold frames all boost growth by sheltering plants from cold, wind and wet. The cloche is the smallest and simplest of these protective structures and is usually moved around the garden from crop to crop as required. I reckon you can spot good gardeners by how fully they exploit this potential. Plonked down in spring, cloches will warm and dry the soil so that sowing can start a couple of weeks sooner.
A cloche can also act as a halfway house so plants sown in the greenhouse have time to acclimatise to the harsher world of the great outdoors. And crops such as peppers, that like a really hot summer, will do better if grown under a cloche right through until harvest. In autumn, a cloche over tomatoes and onions will help them to ripen. During winter, placed over leafy crops like endive and spinach it will improve eating quality, while also helping autumn-sown crops such as spring cabbage to come through winter unscathed.
Cloches were traditionally made of glass, which still has a number of advantages over plastic: it is far better at retaining heat and its weight makes it inherently stable. It also has excellent light transmission, especially important during winter months, and is extremely durable. It is, however, heavy to move about, initially pricey and takes some practice to handle confidently. A simple tent cloche can be made by leaning any two sheets of glass against each other, but far more sophisticated, sturdy and spacious is the Chase High Barn cloche. It uses wire clips to hold four sheets of glass in place and the design is so effective that it remains unchanged 60 years after its introduction.
However, most cloches are now made from plastics. There is a multiplicity of designs and materials, most fairly cheap. The drawback is their limited lifespan as all become brittle and discoloured with prolonged exposure to sunlight - which a cloche will find hard to avoid. My favourite is the Melbourne frame on account of its size, sturdy construction, and unique PVC cover that allows free entry of water and air.
The cheapest option of all is to use lightweight plastic sheeting supported by wire hoops to create a mini polytunnel.
As well as good ventilation, crops growing under cloches need water, which often means tedious lifting and a hosepipe - a good case for installing a permanent seep irrigation system underneath.
The greatest advance has been the arrival of lightweight plastic films designed to be draped unsupported over a growing crop. These "floating" cloches can be perforated plastic films, finely woven netting or fleecy polypropylene. The latter is a real boon and I use swathes of it every year. Unfortunately even if handled and stored carefully it rarely lasts more than three seasons. Fleece is permeable to air and water, so ventilation and irrigation look after themselves. At the same time it gives excellent protection from bad weather, and is so light that it can be left on many crops until they mature. It also gives excellent protection from many insect pests including the dreaded carrot root fly. Almost too good to be true.
Melbourne Frame Cloche available from Jemp Engineering (01753 548327).
Chase Barn Cloche Clips available from Power Gardening Products (01676 523062)
Horticultural Fleece from garden centres and mail order from Agralan (01285 860015)
Tom BarberReuse content