A brief summary of the most popular uses of polytunnels (also known as high tunnels), from vegetable growing to sheltering animals in winter.
The most common use for polytunnels, this is simply a scaled-up version of greenhouse growing. Whether planted straight into the soil or into containers, the tunnel provides a warm and protected environment in which you can grow crops that would otherwise struggle in a lacklustre summer. In the UK that means that you can grow tomatoes, cucumbers, melons, sweet peppers, chillis, aubergines (eggplants) and the like, in greater numbers and with less crowding than you could manage in a small greenhouse.
For homesteading families, having fresh produce to harvest even in the dead of winter is possibly the most important use of tunnel structures. In southern areas the tunnel itself is likely to remain frost-free throughout the winter, but further north some protection with fleece (floating row cover) is needed for tender plants. Even in extremely cold areas such as Maine in the northern USA it is quite possible to continue to crop plants grown in the autumn, using a combination of careful choice of varieties and cloches or cold frames within the tunnel.
‘Hungry gap’ planting
The hungry gap begins when overwintering crops have bolted and ends when new spring plants are finally ready to pick from. This is typically a period when the output of the main garden is small and monotonous, but which is nevertheless all the fresh food there is available. Because of the tunnel’s extra soil warmth, spring and early summer crops can be brought forward by several weeks, and hardy seedlings can be overwintered so that they are ready to go as soon as the temperature rises. With practice, the hungry gap can be eliminated completely. Because local conditions vary so much this requires some experience and careful record-keeping, but when you get it right it is immensely satisfying.
The definition of exotic obviously varies with your location, but using a polytunnel provides a degree of warming equivalent to a full hardiness zone. This means that a tunnel can be used to grow plants that would struggle outdoors, like tomatoes and peaches in the far north of the UK or, in the south, melons and aubergines (egg plant). Garden Organic’s expert gardeners at Ryton in Warwickshire running a ‘tropical tunnel’ experiment were able to grow a wide variety of exotics including guavas, key limes and pomegranates without providing any artifical heat.
With clever use of staging and suspended shelving, your tunnel can be used to module-grow plants for flower beds and hanging baskets in much the same way as a nursery. Bernard Salt, the author of ‘Gardening Under Plastic’ (the first book to cover the use of polytunnels) set aside half of his tunnel to provide his garden with an astonishing variety of flowers throughout the growing season, and even cut flowers for the home in winter.
Animals that are able to retreat to a dry, sheltered environment during cold weather consume less feed, suffer fewer illnesses (and have lower vet’s bills) and are generally happier all round. Chickens are the most common animal to be housed in a domestic tunnel, since they are undemanding and can be kept in even the smallest garden. Although they could be completely confined to the tunnel for the whole winter provided it is well ventilated, chickens much prefer to have access to grass and the bugs in it. With chickens, protecting the sides of the cover from accidental scratches using straw bales is usually enough, but all-polythene tunnels are only suitable for this purpose in winter. During the summer the interior gets much too hot, so for this application you need to use side bars so that your tunnel can have a polythene roof but something more robust, such as wooden slats, for the sides.
Spend a few minutes in one on a cold day and you will soon see why they polytunnels are so popular for protecting patios, swimming pools and hot tubs. While you might not consider getting a tunnel just to provide this function, adding extra length to a tunnel is so inexpensive it is well worth considering some extra space for a seating area or hammock. This rather comfortable looking tunnel (above) is the heart of the Ardvasar Community Permaculture Project on the Isle of Skye, off the western coast of Scotland.