Eat Local: How to Build a Cold Frame
The Ohio State University Extension Office in Cleveland specializes in agricultural issues — they even have a master gardener hotline. So we asked program specialist Andy Hudak how even the most handyman-challenged can extend their growing seasons by crafting a homemade cold frame.
Pre-build: What's a cold frame? It's a device used to extend the growing season, either by starting plants earlier or keeping them in the ground later. Like a greenhouse, it warms a small outdoor area. It differs from a greenhouse in that the only source of heat is the sun.
1| Put away the credit card. You may have everything you need lying around your own home. "The key to the cold frame is a window," Hudak explains. "This spring, I took the plastic wrap over our windows and made frames out of those." Discarded windows work well. So do bricks or cement blocks, or even scrap wood.
2| Put down the hammer. Hudak recommends first-timers stack a pile of bricks into a square, place plants inside the mini fortress and set the window on top. Voila! Cold frame complete. Materials such as bricks and straw (stuffed into the cracks) help insulate plants, and if you build on cement, the floor becomes an instant heat sink. Stack bricks high enough to defend against wind but low enough to catch as many suns rays as possible (around 1 to 2 feet tall).
3| Manage your heat source. "It will get well over 110 degrees in there," says Hudak, "so you're basically cooking your vegetables." Prop your window open during the day, and shut it at night when temps drop to freezing.
Extra Credit: "If you get to the point where you're going to build something out of wood," he says, "build it at an angle. If you picture a solar panel, how it's tilted so it faces the sun directly, the closer you are to perpendicular from the light, the more energy you're getting."