Author Eliot Coleman begins his book "Four Season Harvest" with a story about how, as an April snow falls thickly over his New England garden, he throws on his coat and heads outside to his cold frame to pick a salad. The benefits are obvious. Like a miniature unheated greenhouse, a cold frame enables you to grow a variety of cool season crops, even in winter.
Building a cold frame is pretty simple. You'll need a saw, a drill, a couple of 12-inch boards and one 8-inch board, an old window, screws, and hinges. For simplicity's sake, your cold frame's length and width should match that of the window you'll be using as a lid. The longest 12-inch board will serve as the frame's back. Cut two more 12-inch boards diagonally so that they're 12 inches on one end, angling down to 8 inches on the other — these form the sides. Fasten the sides, back and front together, with wood screws to form a simple, open rectangle. For extra stability, screw L-shaped brackets inside the four corners of your cold frame. Finally, attach an old window to the top of your frame with rust-proof hinges. Use a simple stick to keep your cold frame propped open to let air circulate on sunny days.
Most gardeners can make due with a cold frame. However, the most avid winter gardeners covet the holy grail of winter gardening: a greenhouse. Learn about greenhouses in the next section.