No tool works harder in the garden than a cold frame. Tillers and lawnmowers may make more noise, but their contributions are one dimensional when compared to the efficiency of a cold garden frame.
Cold frames, or garden frames, are simple structures: bottomless enclosures with clear covers. In the past, frames were made of wood and glass, but metal, plexiglass and plastic models are common today.
Garden frames sit on the soil surface or are dug into the earth to absorb the soil’s heat. Covers are generally hinged and tilted, the frames oriented towards the sun like miniature solar collectors. Movable garden frames are convenient, but sunken frames offer greater protection from the cold.
In some ways, a garden frame is more versatile than a greenhouse and is less expensive. Here are ways a gardener can put this tool-for-all-seasons to work.
• Place the frame over deep, well amended garden soil. Sow rows, of cool-season vegetables in early fall. Hardest lettuce, parsley, spinach, radishes, and scallions until mid winter. Stuff straw around plants for additional frost protection.
• Take hardwood cuttings of woody plants in summer and fall. Layer the bundles in flats of peat moss and pack them into the cold for winter storage. Be sure to label the cuttings carefully.
• Place the garden frame in a spot that’s out of the wind. Snow makes a good insulator.
• Overwinter semi-hardy plants such as variegated vinca vine, tender ivy, purple sage and rosemary (use square pots to fit more in). Pack the pots tightly and cover with mulch.
• Convert the garden frame to a root cellar to store vegetables that require cold moist conditions: beet, carrots, celery, leeks, Jerusalem artichokes, rutabagas, parsnips and turnips.
Insulate the sides of the frame with straw bales or insulation board. Cover the vegetables with a thick layer of mulch to keep them from freezing.
• Get a jump on spring planting by starting vegetables seeds early. After germinating seeds indoors, transfer seedlings to cold frames four to six weeks earlier than they could normally be planted outdoors.
• Avoid transplant shock by hardening off flower and vegetable transplants. Two weeks in the frame will help seedlings become accustomed to outdoor conditions gradually.
• Move the cold garden frame to the shady north side of a house or garage to provide a cooler growing environment.
• Take softwood cuttings of perennial flowers and hardy shrubs when shoots are approximately 6 inches long. Pot the cuttings and protect them in the frame until rooted.
• Improve germination of heat-sensitive vegetable seeds by sowing lettuce, spinach and other greens in the frame. Once established, transfer seedlings to the garden for a fall crop.
The simplest garden frames are vented manually. Manual garden frames bear close monitoring, since the temperature can build up quickly inside a frame on warm sunny days. Unvented, plants can be damaged before a gardener has time to act.