Your plant-growing season can start long before warm weather hits—all it takes is a wooden cold frame box with a transparent roof. Here's how to build one of these mini-greenhouses yourself.

The lid is 2 x 2 cedar, grooved to accept a clear acrylic plastic panel. I started by using a power miter saw to crosscut 1 x 8s for the two side panels. For each panel, I cut three 30-inch-long 1 ...

Place the clear acrylic back into the frame, and slide one of the inner box pieces vertically along one side of the frame -- ...