Don’t leave your greenhouse standing empty over autumn and winter. The protection it provides will not only help you to keep tender plants frost-free - it will also let you grow hardy crops, such as salads and herbs, all winter.
An unheated greenhouse can keep overnight temperatures as much as 5°C warmer than outside, which will keep plants frost-free in all but the worst of winters. It will also ensure plants stay dry, which greatly aids survival. A dry plant is much less likely to freeze than a damp one. It is often the combination of cold and wet that kills borderline-tender plants outside over winter.
Just make sure your plants get plenty of light, as natural levels are low in winter. Remove any shading material and clean the glass to maximise the available light.
The following plants are all ideal for growing in a cold greenhouse through autumn and winter.
Try hardy lettuces, such as ‘Salad Bowl’, as well as rocket, pak choi, mizuna, lamb’s lettuce and spinach. Sow in trays or pots of compost, then plant seedlings into large containers, border soil or this year’s old growing bags. Find out more about growing winter salad.
Pot up chives, parsley and mint in autumn and bring them into the greenhouse, where they’ll continue growing all winter. It's worth planting up several pots of each, so you can harvest them in succession for a continuous supply. Watch our video guide to growing herbs in a greenhouse in winter.