Coldframes are a worthy investment of your time and money, but they don’t have to be elaborate, especially for the home gardener. Coldframes are essentially small, simple greenhouses used to extend the gardening season. They can be as elaborate as your budget allows, or as simple as a 4×6 structure using recycled materials. As with any first time gardening project, it’s better to start out small until discovering how beneficial it will be to your gardening. We’ll go over the basics of a coldframe to give you an idea of what you need to assemble your own.
1. Picture a thin raised bed, no wider than you can reach across. For me, that’s about three foot wide, but it may be closer to four foot for others. The length can vary from four to eight foot long, depending on your needs.
2. Unlike a raised bed, a coldframe should be two inches higher in the back. It can be as short as 8 inches or as tall as a couple of feet, but this can vary as long it’s about a two inch difference between the front and back. The rain will run off the top of the frame because of the angle, and it will catch the sunlight more efficiently. 3. The sides of the coldframe can be made out of thick wood, bricks, straw bales, concrete, cinder blocks, or other material. Some people combine materials. For your first coldframe, use what you have on hand, if possible.
4. The top of the coldframe can be made from discarded windows. I put the word out to any friends and relatives with older homes. Often these have to be replaced, and the old ones work perfectly, especially if they attached to the back of the frame with hinges, making it easy to open and close. Other material can be used such as Lucite, Lexan or greenhouse material.
This gives you an idea of how a basic coldframe is assembled. Think of a tilted raised bed covered with windows, allowing the sunlight inside, while protecting plants from the weather. What about the inside of the coldframe? Some gardeners place trays or pots filled with dirt inside the coldframe. Others fill it with good, fertile soil and plant directly into the coldframe.
How does a coldframe protect plants from the cold? Partly by enclosing them in the framed structure, sheltering them from the wind. In the midst of winter the coldframe may need extra protection such as an old carpet laid over the top at night. There are also insulated covers that can be purchased to use for protection if need be.
Coldframes for Beginners Part Two will include tips on where to put your coldframe, heating methods, soil, and how to use it to extend the gardening season.