Cold Frames – The Other Structures for Growing Plants PART 2

* This is part two of a two-part article about “Cold Frames”. Part one can be found here.

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

A cold frame will collect and trap heat by admitting sunlight during the day through its clear plastic/glass covering; and also helps maintain the heat radiated out at night. This almost airtight structure can lessen evaporation losses of moisture as well. The simplest piece of garden tools that employs the principle of a heat and moisture trap is the hotcap, a dome of heavy wax paper used to protect your plants from the frosts.

In planning a cold frame, start with the dimension of the cover. If you are not restricted to a certain size, choose dimensions that will fit some multiple of a standard planting flat. Flats come in several sizes. Make your frame with enough leeway, so you can lift flats in and out without pinching your fingers.

If you want to use scrap pieces of lumber and glass you have on hand, then the size of your cold frame will be dictated by the dimensions of these pieces. You can also buy ready-made window sash, usually 3 by 6 feet, or snap-together aluminum sash in which you install polyethylene plastic.

The walls can be made of scrap lumber, or you can buy the cheapest grade of new lumber. Redwood and cedar are long lasting and rot and insect resistant; other types of wood can also be used if you treat them with a preservative. Either 1 by 12 or 2 by 12 lumber is practical. Fit the corners as tightly as you can; or, to make sure no heat escapes, caulk the edges with asphalt emulsion.

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Since the cold frame is heated by the sun, you must slope the cover toward the south. If you can, build the structure so there is a wall or fence on the north side; you will protect the frame from winds and cut down on loss of heat. To increase the light level within the frame, paint the fence or wall a light color or paint the cold frame interior sidewalls white or silver. Wherever location you choose for your cold frame, make sure it is not in a part of the garden that has poor drainage, since you don’t want water to collect in or around the frame

Placing a good thermometer in your cold frame is very important if you want your cold frame gardening succeed. Most plants that will grow well outdoors in North America will continue growing at temperatures from about 40° F to 100° F and do best at about 85° F, you can prop open the top of the frame to let out some heat. Then in late afternoon, when the outside temperature starts to fall, shut the top to trap the heat radiated by the surrounding soil. In really hot weather, you will have to whitewash the glass or make a second cover of lath to cut down on the light.

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

Cold Frames

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