|Cold frame in use|
Anyone can build a cold frame with little or no cost; they are easy to build from recycled materials. I made my cold frame out of two old windows I got for free, and scraps of lumber I had in the garage.
A cold frame is simply a box that is higher in the back than the front, with a clear top and open bottom. The top can be made with an old shower door, patio door, windows, clear plastic, or any other durable, transparent material. The base of the cold frame could also be made out of several types of recycled materials such as wood, cinder blocks, brick or straw bales. The size of the box will be determined by the size of the top. The bottom of the cold frame is open and it either sits on top of the ground, or can be buried into the soil a few inches. There are many different design plans available on the internet.
The best location to place a cold frame is facing south or west. Putting the cold frame up against a structure such as a house, garage or fence will offer more protection and keep the cold frame warmer at night. On extremely cold nights, the cold frame can be covered by a blanket to help keep the heat in.
|Venting the cold frame|
In my experience, the biggest challenge of using a cold frame is venting it. A cold frame must be vented to release excess heat and keep the seeds or plants from overheating. It's amazing how hot it gets in there on a sunny day, even if it's cold outside.
You can vent the cold frame manually by propping open the lid on sunny days, and closing it on cold nights. Otherwise an automatic vent controller could be purchased, which will open and close the lid at specific temperatures. It's a good idea to keep a minimum-maximum thermometer in the cold frame to monitor the temperature fluctuations.
|Cold frame with windows removed|
Cold frames are an easy and inexpensive way to extend your growing season. Every gardener should give cold frame gardening a try.