Tips For Heating A Greenhouse In Autumn / Winter

The cold weather is coming…and that means heating your greenhouse is essential.

Greenhouse heating not only protects tender plants from frosting, it also keeps young plants protected until the spring time.

Heating a greenhouse however, can be an expensive luxury, and nobody likes the idea of wasting money on energy… so we’ve put together some top tips to help you keep your costs down and make your greenhouse heating that little more efficient.

Bubble Wrapping

A layer of bubble wrap clipped to the inside of your greenhouse frame will reduce heat loss sufficiently and block icy winter draughts. Even if it’s unheated it will benefit from bubble wrap.

Its best to buy purpose made horticultural bubble wrap from garden centres though, as this will let in more light. You can also use it to wrap outdoor pots, which will prevent them cracking in icy conditions.

Invest In A Greenhouse Heating System

Electric fan heaters are ideal if you have a mains power supply to your greenhouse. They are particularly good for moving air around, which helps prevent cold spots and reduce the risk of disease.

Don’t have a mains power supply? The use a paraffin heater.

It’s also advisable to speak to an expert on such matters, just to check the most cost effective way for you.

Use The Thermostat

You can save a lot of money, time and energy by only heating your greenhouse when necessary. Most electric greenhouse heaters come with a built in thermostat so you can set your greenhouse heater to only come on when temperatures drop below a certain point.

Handy right!?

Choose The Correct Temperature

The majority of greenhouse plants do not require tropical conditions, so don’t waste energy on maintaining high temperatures. A minimum temperature of 2C (36F) will keep it heated and frost free.

If you have more tender plants like pelargoniums, fuchsias and citrus trees, they may require a temperature of 7C (45F), so keep the temperature at around 4C to accommodate them and the rest of your plants.

For particularly delicate plants, you may need to increase the temperature to a minimum of 13C (55F).

Ask a horticulture specialist or a local gardener for tips and advice on the best plant groupings. Alternatively you can partition your greenhouse to only heat various areas.

Use A Good Thermometer

Invest in a good thermometer with both minimum and maximum readings. By keeping one eye on the temperature you’ll be able to use your greenhouse heater more efficiently, adjusting it when it’s necessary.

Be Careful With Heaters

Electric fan heaters are best in an open, central spot at one end of your greenhouse – away from contact with water.

In some instances you may need to angle the heater slightly to direct the airflow above plants that are stood close by.


On particularly cold nights, fleecing provides several degrees more protection to your plants (without having to turn up the thermostat).

The best time to do this is overnight when temperatures drop. So during the day, if it’s just a little nippy, remove the fleecing so they receive adequate light and ventilation.


One drawback of heating your greenhouse is the problem of increased humidity. Many green fingered enthusiasts claim this to be one of their biggest ‘bugbears’, and find it hard to handle – especially in the winter.

Good ventilation is essential to prevent the spread fungal of diseases and maintain a healthy growing environment.

You can prevent moisture from building up by watering plants sparingly, and early in the day.

Clear condensation by opening greenhouse vents on warm sunny mornings, then close them again before the sun goes down. This helps trap the daytime warmth in the greenhouse and keep it warmer for longer.