The days are getting shorter now and the nights are cooler, so if you have a greenhouse that you use to overwinter plants, it’s time to make sure it’s winter ready.
Although an unheated greenhouse can drop below freezing in cold weather, it still offers protection, especially to plants in containers that dislike being too wet over winter. Pots of cordyline, agapanthus and other borderline hardy plants will often get through winter better in a greenhouse than when left outside in the wind and rain.
If you’re able to give a little heat to protect from the frost, the sky' s your limit as you’ll be able to overwinter a wide range of plants without too many problems. Plants such as pelargoniums, fuchsias, streptocarpus, cacti, succulents, citrus and many other tender perennials will tick over nicely if you can maintain a temperature of 5C (40F).
The most economical way to do this is to use an electric heater that is thermostatically controlled and will cut in when the temperature drops below the set temperature. Keeping the greenhouse well insulated also helps a great deal by cutting out cold draughts and by retaining warmth on days when the sun does shine. With a small heater and good insulation you’ll find the heating costs over winter are not that expensive.
If you don’t have bubble insulation, consider fitting it. If you do have it, check it’s secure and well fitted.
A maximum-minimum thermometer is essential to record high and low temperatures.
If heating the greenhouse, test the heater and regulate it with the max-min thermometer.
A heater bench made using soil-warming cables gives off heat and can house tender plants.