Greenhouse
Structure
A greenhouse is the most flexible way to extend the growing season in the UK, giving a protected place for sowing, raising and cropping plants. Even an unheated greenhouse can transform spring and autumn growing, while a heated one supports more dependable year-round propagation and winter use.
How it works
Glazing traps solar warmth and shelters plants from rain, wind and overnight temperature drops. This produces a warmer, more stable microclimate than an open bed, although temperatures can still fall close to outdoor levels in winter. Heat, insulation and thermal mass increase protection, but successful greenhouse growing also depends on air movement, regular watering and summer shading to prevent excessive heat and humidity.
Best for
Grow tomatoes, cucumbers, peppers, chillies, aubergines and early courgettes under cover, as well as grapes, peaches and tender ornamentals where space allows. Use benches for module trays of salads, brassicas and annual flowers. An unheated greenhouse also suits overwintering tender container plants and growing winter salad leaves in pots or borders.
How to use it
Place the greenhouse in the sunniest practical position, away from shade and exposed wind. Clean the glazing before spring, check vents and make sure water is close by. Sow hardy plants in module trays from late winter, then introduce heat-loving crops only when nights are reliably mild or with suitable protection. Open doors and roof vents on warm days, water at the root in the morning, and use shade netting during hot spells. Remove spent crops promptly and keep paths clear for good airflow.
Tips
A maximum-minimum thermometer helps reveal cold nights and overheating. Do not seal a greenhouse tightly: ventilation reduces disease pressure and strengthens plants. Keep pots off cold ground in early spring, and insulate tender crops temporarily with horticultural fleece when a late frost is forecast.
Greenhouse: frequently asked questions
How does greenhouse work?
Glazing traps solar warmth and shelters plants from rain, wind and overnight temperature drops.
How do I use greenhouse?
Place the greenhouse in the sunniest practical position, away from shade and exposed wind.
What is greenhouse best for?
Grow tomatoes, cucumbers, peppers, chillies, aubergines and early courgettes under cover, as well as grapes, peaches and tender ornamentals where space allows.
General guidance for UK gardens and allotments. Page updated 19 Sep 2026.