After a long winter, it takes too much guesswork and patience to wait for the last frosty night before setting out tender plans that were started under LED grow lights in the basement back in February. In past years, we often had to deploy sheets, buckets and pots to protect plants in the garden from one or more late-breaking frost events. This year, we decided to a) be more patient and b) build four cold frames for setting out early plants like radishes and cool-loving lettuces.
The cold frame design we settled on is a 2′ x 4′ x 18″ high box with a hinged lid and surrounded by the same corrugated polycarbonate that we used in The Cottage / Greenhouse project a few years ago. Available in either 2′ x 8′ or 2′ x 12′ panels from Home Depot, this clear material is impact resistant and has held up well in the garden shed. The other design criteria was for the assemblies to be light enough to move easily, so the internal frame components for all four assemblies were all made from a single 4′ x 8′ sheet of AC exterior grade plywood. A couple of coats of exterior paint will hopefully help to protect these cold frames for many seasons of use.