How to Construct a Cold Frame
Most gardeners wish for a longer growing season. A cold frame, which is a bottomless box with a glass top, can help provide this. A cold frame is placed over a part of your garden; the window in the frame magnifies the heat of the sun and the box holds the heat in. It's not uncommon for an area covered by a cold frame to be 10 to 15 degrees warmer than the ambient air temperature. Does this Spark an idea?
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Things You'll Need
- Wooden window frame
- Plywood
- Galvanized screws
- Screwdriver and/or drill
- 2-by-2 foot board, 3 to 4 feet long
- Small wood saw or hack saw
Instructions
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1
Measure your window frame. Use these measurements when cutting your walls in step 2.
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2
Mark the plywood and cut the four walls. The longer side walls should be the same length as the longer side of the window frame. The shorter front and back walls should be the same length as the shorter side of the window frame. For height, make the front wall 8 to 12 inches shorter than the back wall. Make the side walls shorter on one side so they line up with the height of both the front and back walls.
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3
Attach the walls of the cold frame to each other using two to three galvanized screws at each corner.
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4
Lay the window frame on top of the cold frame. Place the hinges at each end of the back wall, about 6 inches from the ends. Use galvanized screws to attach.
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5
Use a small wood or hack saw to cut a 1-inch notch about 2 inches from one end of the 2-by-2. Hook the notch over the top edge of the front of the cold frame and place the other end in the recessed area next to the glass on the window frame. When the cover is open, the prop rod should be inserted in the topmost part, secured in the recessed area where the glass is.
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Tips & Warnings
Make a series of notches along the length of your prop rod; you'll be able to prop the cover open as much or as little as you want simply by using a different notch. Be sure to provide a means to prop open the top of the cold frame; daytime temperatures in the 40s when the sun is shining can heat up the interior of the cold frame enough to burn your plants.
Keep an eye on the weather when using a cold frame; prop open the top if daytime temperatures are in the 40s or higher and on sunny days. Remember to close the cover at night until nighttime temperatures stay above 45 degrees.
