Providing just a little heat is all that’s needed.
A greenhouse is a real asset in the garden and provides you with a place to garden all through the year. By providing just a little heat through the winter months you can easily grow a wide range of plants that wouldn’t survive in a cold, unheated greenhouse.
All that is needed to keep a range of tender plants is a little gentle heat to provide frost-free growing conditions. A small electric fan heater with a build-in thermostat is ideal set at around 5-6oC (40-42oF). When the air temperature drops below this, the heater will switch on and supply warm air. This is a very economical way to heat a greenhouse and keep plants frost free at night. In these conditions you can easily grow a range of tender foliage and flowering plants to create a colourful display in the greenhouse over winter. As winter goes on you many need to change and swap some of the plant around as they either finish flowering, or come into flower, but with a mix of interesting foliage plants you can easily have plants that will look good from now right the way through the winter.
Not only will the plants look attractive, it also gives you somewhere to potter around over the winter months when the weather is too cold and wet to work outside.