Here are tips on how to make cold frames for the garden.
What is a Cold Frame?
Cold frames are usually bottomless boxes that are set over plants in the garden to protect them in adverse weather. They are usually built low to the ground and have a transparent roof with a hinge.
Why Use a Cold Frame?
Cold frames protect plans from the wind and also retain heat. Gardeners use cold frames to extend their gardening season—to get a jumpstart in the spring when seeds are sowed or to prolong the season in the fall for a couple of weeks. Cold frames are also used to “harden off” seedlings that were started indoors.
- Try sowing seeds of crops such as radish, lettuce, endive, and scallions directly in the frame for an early or late harvest.
- You can even raise them there all summer as long as the cover is removed when warm weather arrives.
- Consider growing winter lettuces of other salad leaves.
How to Make a Cold Frame
- Frames can be bought constructed from timber and plastic but concrete blocks or bricks can also be used.
- You can even construct a bottomless wooden box and set it in the garden or atop other good soil in a sunny location.
- Top the box either with glass (perhaps an old storm window) or a frame covered with clear plastic.
- Hinge the cover or add a sliding lid so that it may be opened for ventilation on warm days.
- If you have high-sided raised beds, you could add a sheet of glass on top to construct a temporary cold frame.
- Temporary frames or “cloches” can also be made by leaning old storm windows tent-style over the plants along the length of the garden row.
- To protect individual seedlings, cut the bottoms out of plastic milk jugs and place them over individual plants, holding the jugs in place with mounded soil. During sunny days, remove the caps for ventilation.
A Hot Bed
A hot bed is a cold frame that is heated. The method of using horse manure or compost works well and is more economical than electric heating cables.
- For a nonelectric hot bed, excavate 18 to 24 inches under the frame and add fresh manure or compost.
- Turn and moisten this material every couple of days for a week until it settles, then cover it with 6 inches of soil.
- As the manure or compost decomposes, it will generate enough heat to protect against early or late frosts.