A cold frame is essential for any gardener who wants to be able to extend the harvest beyond the typical growing season. By lengthening the period when vegetables can grow by at least a month at either end of the season, a cold frame is a simple and effective way of allowing you to get a lot more from your garden. Ideal for both serious gardeners and even novices who would like a greenhouse but lack the available space, cold frames are a cost effective means of providing an abundant harvest, and there is little wonder they have been popular with gardeners for centuries.

What is a cold frame?

wooden cold frameA cold frame consists of a bottomless box that has four sides and a glass roof, although these days a polycarbonate roof is more typical. The four walls trap heat and give the plants shelter, while the transparent lid admits light. The wooden cold frame from sheds.co.uk also has polycarbonate glazing in the walls, which allows for the maximum possible amount of light to enter the frame.

A standard cold frame is shaped so that the back wall is a few inches higher than the front wall. There are two reasons for this. Firstly, having an angled roof maximises the amount of light that is able to get in. Secondly, with the roof being pitched in such a way, rainwater and melted snow drain off easily.

How do cold frames work?

The effect of a cold frame is to create a microclimate that raises the temperature of the air and soil several degrees higher than the outside. This means that any plants within the frame will be saved from the worst effects of the cold weather. It is not a greenhouse however, and won’t help you to grow tropical plants all year round. But it is certainly the case that any cold-tolerant crops can get a great deal of benefit from being planted in a cold frame, particularly in the cooler seasons.

Where should I place my cold frame?

The best place to position your cold frame will be one that gets plenty of light. Some shading during the day will be okay, but try and place your cold frame in a south-facing position if you can, so that it receives as much daylight as possible. Also, it’s a good idea to keep it protected from the wind, if you can. Remember that cold frames do not have a bottom, so put yours in a place that has good drainage.

What can I grow in a cold frame?

Different plants will prosper in a cold frame at different times of the year. During the colder seasons, you can extend the harvests of many kinds of vegetables with a cold frame, particularly cold tolerant crops like carrots, spinach, leeks, onions and also salad ingredients like lettuce and radishes.

Cold frames are also very useful as a kind of halfway house between the greenhouse and the open ground. Many gardeners use their cold frame to acclimatise seedlings that have sprouted in the warmth of the greenhouse before they are ready to be transplanted to the open ground. During the warmer seasons, make sure your plants don’t get too hot. It’s a good idea to keep the cold frame well ventilated. For more details, our range of cold frames.

Image resources:

  • www.corvallisindoorwintermarket.blogspot.com
  • www.towerofhanoi.net