Polytunnel
Structure
A polytunnel offers a generous covered growing space for less cost than many glasshouses, making it a favourite on UK allotments and productive gardens. Its polythene skin protects crops from chilling wind and heavy rain, enabling earlier planting, later harvests and a wider range of warmth-loving vegetables.
How it works
The polythene cover captures solar warmth while the tunnel structure blocks wind and rain. Soil warms earlier in spring, and plants avoid the cooling effect of wet foliage and exposed conditions. Temperatures can rise rapidly in sunshine, so doors and side vents must be managed carefully. The cover also keeps rain off the soil, meaning watering and soil moisture need deliberate attention.
Best for
Polytunnels are ideal for tomatoes, peppers, aubergines, cucumbers, French beans and early potatoes, alongside long rows of salad leaves and herbs. They suit gardeners who want a productive protected plot rather than just propagation space. They are particularly helpful in cool, wet or windy areas, and on allotments with sufficient room and permission.
How to use it
Choose a level, open site with reliable access to water, then anchor the structure carefully according to its design and local wind exposure. Improve beds with garden compost and rotate crop families where possible. Start hardy salads and brassicas early, then plant tender crops after the risk of severe frost has eased. Open both ends whenever conditions are mild, water deeply at the base, and avoid overcrowding. In autumn, clear tired summer plants and replant beds with winter salads, spinach or hardy herbs.
Tips
Secure every cover and door fastening before autumn gales. In summer, ventilation is more important than trapping heat, so open early each morning. Watering is often needed more frequently than expected because rainfall is excluded. Keep a dedicated path to avoid compacting productive soil.
Polytunnel: frequently asked questions
How does polytunnel work?
The polythene cover captures solar warmth while the tunnel structure blocks wind and rain.
How do I use polytunnel?
Choose a level, open site with reliable access to water, then anchor the structure carefully according to its design and local wind exposure.
What is polytunnel best for?
Polytunnels are ideal for tomatoes, peppers, aubergines, cucumbers, French beans and early potatoes, alongside long rows of salad leaves and herbs.
General guidance for UK gardens and allotments. Page updated 18 Sep 2026.