Most gardeners know what a cold frame is, but few use it for more than hardening off seedlings in spring. I don’t use a cold frame for hardening off because it shelters seedlings from breezes, and they must get used to those as well as direct sunlight and chilly nights. Many other gardeners also use cold frames in which to grow frost-tolerant plants over much of the winter. Plants such as lettuce, cabbage, collards, kale or broccoli can be successfully grown throughout one of our mild winters in a cold frame.
Perhaps more useful in winter is a hotbed, if you don’t resort to high tunnel growing. If you have horses or have a friend who has horses, a hotbed can be fairly easy. A hotbed is a cold frame over a hot pit, essentially. Dig a pit the size and shape of your cold frame, to a depth of 30 inches. Then mix fresh horse manure with straw in this proportion: one-third straw to two-thirds horse manure, in a pile near where you’ll site your cold frame, and mix that pile. If manure has dried, wet it down with water, but don’t drown it. You want that pile to begin heating up. This manure mix should be started about 10 days before you put it into the hotbed.
This pile should begin heating up in three or four days, and then turn the pile by moving the outside edges to the inside, and the inside to the outer edges. Once the entire pile is heating, then shovel manure into the pit, to a depth of 6 inches, then tamp it down, then other layers, each 6 inches deep and tamped down until you’re 6 inches from the top of the soil. Then top all with rich fine sifted garden soil or compost, and place the cold frame on top. The heat of the decaying manure and straw should kill any weed seeds in your soil mix.
Delay planting in the now hot “cold frame” until the soil temperature has dropped to 85 degrees or cooler. This heated effect will last for weeks, but probably not all winter. The heat will be variable and uncontrollable, even though the cold frame is atop, holding heat in.
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Another way to build a hot frame is to bury an electric heating cable in your soil. I bought one years ago, and a friend used it, but I never had a space available near an electric outlet. When I did buy that one, the pack contained no instructions, so I’d guess that would still be the case. If I were using a heating cable, I’d be careful to wind it back and forth so that it didn’t touch itself.
This has been a disappointing growing season for tomatoes. If your tomatoes are late ripening, do not cut foliage to give them more sun exposure, because that risks sunburn that destroys fruit. Tomatoes do not need sun exposure to ripen. They will ripen in their own time. Next year, pay heed to the “days to maturity” description on a tag or catalog description. That is days to fruit ripeness after transplant, and 90 days or more is late maturity, 75 to 90 days medium maturity, and 55-75 are considered early ripeners.
Test your winter squash with a thumbnail. If it doesn’t penetrate more than a sixteenth of an inch, I harvest a squash, even though it still hasn’t reached its full color. Be sure to harvest at least 2 inches of the squash’s stem unless it’s one of the huge Hubbard squash. If a butternut, climbing zucchini, or delicata, for instance, is harvested without a stem, use that one first, for it won’t keep as well as squash with stems intact.
Harvesting these now may permit setting a second crop of squashes from the same vines.
Pumpkins, close relatives of squash, may be left on the vine through a light frost if you dare (I wouldn’t, for the frost may kill the vine but not the pumpkin.) It may create frost patches on the exposed part of the pumpkin that will be vulnerable to disease, shortening its storage life. I harvest all if there’s a frost forecast.
Keep a close eye on sun exposure for all of your garden beds. Exposure changes, due to shrub or tree growth or removal, in your or a neighbor’s yard. Increased shade may prevent flowering, or increased sun on shade lovers may sunburn leaves.
Send garden questions to firstname.lastname@example.org or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.