An unheated greenhouse can maintain an overnight temperature around five degrees higher than outside, so ditch the expensive and environmentally unfriendly greenhouse heaters this winter and grow cold. Here’s how…
- Dry as a bone. Keep the greenhouse and plants dry and water sparingly. Clean your greenhouse thoroughly so you know there’s no diseases, bugs (or moisture) lurking.
- Crisp and even. Maintain an even temperature so your plants don’t produce lots of leafy growth or get frostbitten. Instead of energy sapping heaters, try insulating your greenhouse in bubble wrap or add a rudimentary ‘heat sink’. Piles of bricks, sunk into the ground, will absorb heat in the day and release it at night.
- Bright and breezy. On sunny days, open the vents and doors to allow air to circulate and on cold nights keep leaves away from the glass panes so frost doesn’t penetrate them. Take away shading completely to allow for optimum light levels.
- Get growing. Try veg and fruit that tolerate lower temperatures: winter salads and oriental leaves such as Chinese Cabbage, mustard ‘Red Giant’, Tatsoi and Komatsuna or hardy herbs such as chives, parsley and mint. Try forcing rhubarb indoors by bringing a (frosted) crown into the greenhouse and covering with an up-turned bin to exclude light: by January, you could be picking tender, sweet pink stems!