Why Grow Under Cover?

 
In areas where the ground warms up slowly, or temperatures stay cold and the day-length is short, growing plants undercover is a great way of extending the growing season and therefore increasing productivity.

In fact the growing season can often be lengthened by up to two months, and the shelter provided as well as higher temperatures increases yield and quality significantly.

Growing under cover in the early spring enables plants to be started earlier, and some, can continue growing and cropping later into the winter for example peas or brassicas if given protection.

Green Houses and Poly Tunnels
Immediately when talking of growing undercover people think of greenhouses and poly tunnels. These are excellent for many

vegetables. They provide an easily controlled environment, they retain heat at night and can be ventilated during the day.

Poly tunnels tend however to be slightly more difficult to control than greenhouses but are cheaper to buy.

The soil within a greenhouse / poly tunnel may require replacing or sterilising every few years to prevent build up of harmful pests and diseases.

During summer months ventilation is key, otherwise temperatures can soar quickly, and plants may dehydrate or even be scorched by the sun.

Greenhouses, poly tunnels and cold frames for me are ideal tools for starting plants early in the season, and growing them on until the danger of frost has passed, and the average daily temperature is over 6 degrees. It enables earlier cropping and increases the amount of crops you can grow. They are also great for growing tomatoes!

Cloches 
There are a variety of types of cloches, continuous cloches, tunnel cloches or floating cloches.

When using cloches it is important that the ground has been well cultivated, free of weeds and it helps if there is a mulch too as these suppress weeds and retain moisture. Cloches can be made from polythene, flexible plastic, rigid plastic, or glass. and can vary in size. The principal is the same with each. They help to warm the ground, offer protection from the wind, and enable the lengthening of the growing season.

Small cloches may not need watering, rainwater may reach them from the sides and condensation from the inside may drip down and keep the ground moist. Larger cloches will have to be removable to allow watering.

A floating cloche is a floating sheet of fleece or clear perforated plastic which is laid over crops after sowing. Rainwater is able to pass through and the sheet rises as the plants grow in height. These floating cloches can provide up to 2 degrees of frost protection.

Frames
Cold frames are not as portable as cloches and tend to be more permanent fixtures. Often built with brick or wooden sides with an angled (5 -15 degrees) transparent opening lid that can closed or opened to various degrees. This is usually glass but plastic is just as effective. Frames are similar in use to cloches and can be used for germination, propagation, growing on or hardening off of plants. Sometimes they are heated.

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