There are different types of materials used for cloches. Glass is the best choice if you are going to use the cloches extensively and moved from crop to crop. A good alternative is clear plastic material, but even they are less expensive than those made of glass, they do not allow such good light penetration and also they do not retain as much heat or last as long as in a glass cloche. Clear plastic material can be made of PVC, polypropylene or polycarbonate. PVC is thicker and more rigid than polypropylene. Polypropylene is used in some injection-moulded cloches and in corrugated sheets. Cloches made from twin-walled polycarbonate offer good insulation and should last for at least ten years.
Any cloche should have end pieces because without them a cloche may become a wind tunnel. The end pieces should fit well to preclude draughts but they should be easy to remove to provide ventilation when needed.
If you want to build your own cloches you can construct a tent cloche. This is easy and inexpensive to construct. They are made of two sheets of glass held together by a wire or plastic clips to form a tent shape. This type of cloche is mainly suitable for germinating seeds, protecting young seedlings in spring and for low-growing plants.
Tunnel cloches are made from either rigid or flexible plastic. Used mainly for strawberries or early carrots, flexible plastic cloches are made of plastic sheets supported by wire hoops and tensioned with wires. For a longer resistance in time is best to use a heavy-duty plastic that has been treated with an ultraviolet inhibitor. Rigid models are more attractive and easier to move around but more expensive than flexible ones. Some tunnel cloches have self-watering features.
Another type of cloche is the barn cloche. This has almost vertical sides supporting a sloping, tent-shaped top. Because of its extra height it is mainly useful for relatively tall plants. More expensive than a tent cloche, this cloche has models made of glass or rigid plastic with lifting or removable tops to provide ventilation to the plants in warm weather while still offering wind protection. This makes weeding, watering and harvesting easier.
Wall-of-water cloche is an unusual design of cloche that is useful for single plants and consists of a circle of clear plastic tubes into which water is poured. The tubes form the wall of the cloche which alters in shape depending on the water level. The water protects the plant from several degrees of frost.
Using cloches makes watering difficult, but a self-watering cloche design will allow rainwater to trickle through gradually to the plants below. Alternatively it may have a tubular system that is connected to a hosepipe.
For early sowings and small plants that only need protection from one or two degrees of frost you can use floating cloches. These consist of a sheet of perforated plastic sheeting or polypropylene fiber fleece which is placed over the ground where the crops have been sown. They are permeable, allowing rainwater to penetrate to the soil below and also allow air to pass freely through the material. The sheets or fleece should be anchored firmly into the soil at the edges of the beds with soil, stones or pegs.
For protecting individual plants in the early stages of growth or any vulnerable, small plants during winter you can use individual cloches. You can buy some attractive ready-made, rigid plastic or glass bell or dome-shaped but they can be quite expensive. These have curved walls from which condensation trickles to the ground rather than falling on the plants. You can make yourself some individual cloches such as waxed-paper protectors and cut-off plastic bottles. They are easy to make and much less expensive than the ready-made ones available for buying.