In the early spring, a cold frame can be as valuable to the gardener as his or her right arm. During the rest of the year, however, one of these little hothouses just takes up needed growing space and-in anything other than a specialty gardenis usually in the way.

You can solve this seasonal dilemma, though, if you build yourself a knockdown cold frame ... which can be set up in minutes when it's needed and taken apart just as quickly (to be stored in the garage or wherever) after warm weather or seedling maturity make the protective enclosure unnecessary.

One of the biggest advantages of the knockdown cold frame is the adaptability of its very basic design. These structures can be built in about any size that you'd want ... either to make use of available materials or to fit in a particular corner of your garden.

Of course, you'll have to remember to allow enough inside height in your cold frame for whatever plants you intend to grow, and to slope the cover toward the front so that rain water can run off. Be certain, too, that the cover panel fits tightly over the frame (to prevent cold drafts that could injure delicate seedlings) and that you position your finished cold frame-especially in early springso that its slope faces south and can capture as much of that precious sunshine as possible.