How warm your greenhouse is kept during the colder months of the year will be an important factor in which plants you grow and how early you can sow. Robert Hall explains the best ways to heat your greenhouse over the winter.
A minimum temperature of 7C is needed to keep most tender plants happy, so you must think about insulating and heating the greenhouse if you want to make the most of it throughout the year.
The best way to conserve heat is Bubble Insulation that comes in a bulk roll measuring 30 metres long and .75 metre wide. It's quite easily fixed inside the greenhouse, preferbly leaving a gap of about an inch with the glazing, and this cheap method can reduce heat loss by as much as 50%.
There are three main alternatives for greenhouse heating, electricity, gas or paraffin, each of them has advantages and disadvantages.
These heaters can be economical to buy but, without a thermostat, temperature control is difficult and they need daily maintenance with frequent re-fuelling. Other disadvantages are that humidity and condensation might be a problem and toxic fumes, that can be harmful to plant health, may be emitted.
Propane, butane, even mains gas are easy to use although again harmful fumes may be a problem. Initially more expensive than paraffin, gas can be controlled by a thermostat and high temperatures may be obtained if required. You always need a spare gas cylinder at hand.
Easy to use and reliable, electricity is clean and doesn't create any odour or fumes. Again high temperatures can be achieved and controlled fairly accurately, and cost effectively, by a thermostat. Fan heaters provide more uniform heat and can be used to cool the greenhouse during the summer.
Whatever your choice, paraffin, gas or electricity used in combination with bubble insulation will expand your gardening horizons. Greenhouses are a serious purchase and deserve to be used all year round, with heating and insulation this can be achieved.