"Timing is everything"—the old aphorism applies in the garden as much as anywhere else. That's because in most parts of the country, the growing season only lasts for the handful of months between the last spring frost and the first hard frost in fall. To give themselves a wider window of opportunity, many gardeners rely on cold frames like this one. By warming and sheltering the plants under its cover, a cold frame typically extends the growing season by a couple months (or even longer if you live in a warm region). You can design and build your own cold frame, of course, but there's also always the option of buying a ready-to-assemble kit online. Available at Amazon; $55.99.