The Winter Months
In winter the greenhouse need not be put to sleep. It’s a useful convalescent home for any tender plants that you may need to overwinter and even in an unheated space they will be protected from frost. Bubble wrap or horticultural fleece can also help to provide a protective micro-climate around these tender species.
Cut and come again lettuce, spinach, herb and salad leaves can also be successfully maintained in an unheated greenhouse to maintain a steady supply of fresh produce without the need for a dash to the supermarket.
As the days shorten you need to maximise light levels. Open blinds or remove any shading added over the summer, sterilise or disinfect any staging or fixtures to remove or reduce the threat of disease and check the heating system if you have it.
For smaller structures heating systems may not be realistic but bubble wrap can help to insulate individual plants or young seedlings. Keep an eye on the weather as first frosts can come by surprise. Inspect any plants you bring into the greenhouse for disease or virus infection and in general reduce watering levels to keep the threat of mould or mildew to a minimum.