Winter is the greenhouse’s hardest season: cold, low light and the constant risk of damp, disease-friendly air. But with a few adjustments it earns its keep — overwintering tender plants, growing hardy crops and getting a head start on spring. Here’s how to manage it.
The winter challenges
- Cold — hold your target minimum (frost-free for most); see heating and temperature.
- Low light — growth slows; keep glazing clean and don’t overcrowd; grow lights can help.
- Humidity & disease — the big winter killer; trapped moist air breeds botrytis.
Winter management
- Insulate the glazing with bubble wrap to cut heat loss.
- Ventilate a little on milder days and keep a circulation fan running — airflow prevents disease. See humidity.
- Water sparingly, in the morning, at the base — plants use little in winter and wet, cold compost invites rot.
- Group tender plants and protect with fleece on the coldest nights.
What to grow
Hardy salad leaves, winter greens, garlic and overwintering hardy/half-hardy plants suit a cool or frost-free greenhouse. Tender and tropical plants need a warm greenhouse. See greenhouse plants and unheated greenhouse.
Quick questions
What’s the biggest risk to greenhouse plants in winter? Damp, stagnant air causing disease — often more damaging than the cold. Ventilate a little, keep air moving and water sparingly.
