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 Cold frames and Hot bedsA coldframe is a protected plant bed. It has no artificial heat added. The temperature difference between the inside and outside of the frame is generally not more than 5 to 10 degrees. A mat or blanket may be placed over the frame on cold nights to conserve heat, but this increases temperature by only a few degrees. There are times, however, when a few degrees can be very important.
A coldframe is used to provide shelter for tender perennials, to "harden off" seedling plants or to start cold-tolerant plants such as pansies, cabbage or lettuce earlier than they can be started in open soil. It may also be used to overwinter summer-rooted cuttings of woody plants.
A hotbed basically is a heated coldframe. In many ways it is a miniature greenhouse, providing the same benefits with limited space at minimal expense. It is a means for extending the growing season. It is most often used to give an early start to warm-season vegetables such as tomato, pepper or melon. It may also be used to root cuttings of some woody plants.
Cold frames and sun boxes rely on the sun for their sole source of heat. Hot beds are heated by soil-heating cables, steam-carrying pipes, or fresh, strawy manure buried beneath the rooting zones of the plants. Heat is collected by all these frames when the sun’s rays penetrate the sash made of clear plastic, glass, or fiberglass. The ideal location for a coldframe is a southern or southeastern exposure with a slight slope to insure good drainage and maximum solar absorption. A sheltered spot with a wall or hedge to the north will provide protection against winter winds. Sinking the frame into the ground somewhat will also provide protection, with the earth for insulation. To simplify use of the frame, consider a walkway to the front, adequate space behind the frame to remove the sash, and perhaps weights to make raising and lowering of glass sashes easier. Some gardeners make their cold frames lightweight enough to be moved from one section of the garden to another. |
