A walk-in polytunnel protects crops from wind, cold and heavy rain just like a cloche, but forms a more permanent structure. Its larger size gives it the advantage of being able to house a large number of plants.

Polytunnel kits come in a variety of sizes; 3-5.5 m (10-18 ft) wide and 3-20 m (10-65 ft) long. They usually come supplied with 720 gauge polythene that has been stabilised against ageing from ultra-violet light, which means that is should last approximately 4 years before it needs replacing. The life of the cover can be extended by using anti-hot spot tape, which stops heat from the metal frame causing weak spots in the polythene.

Method

1. To avoid the polytunnel becoming excessively hot in summer, it is best to position it so that its longest side runs from north to south. Mark out the site carefully with a builder's line, making sure that the corners are correctly aligned so the final tunnel is straight.
2. Make sure that the ground is thoroughly clear of weeds as they will grow very fast once the tunnel is erected.
3. Dig a trench and insert the provided foundation tubes into the ground.
4. Place each hoop into position, and slot them together at the top.
5. Apply anti-hot spot tape to the top of the hoops.
6. It is best to apply the polythene cover on a warm day - the sheeting should be opened up and allowed to warm up so that it is flexible enough to be pulled taut over the frame.
7. Pull the polythene cover over the hoops and anchor the edges down by burying them in the trench.
8. Assemble the door frame as instructed by the kit, making sure that any rough sawn timber edges do not cause snags in the cover.
9. Apply a layer of organic mulch to conserve water and suppress weeds.
10. Inspect the cover regularly and repair any rips with special tape.