Growing Vegetables in a Cold Frame or Hot Bed
Imagine harvesting fresh lettuce, spinach, radishes, green onions and other vegetables from your own garden this winter. In fact, you could have a fresh homegrown salad for Thanksgiving or Christmas. Yes, it's possible, if you grow your own vegetables in a cold frame or hot bed.
Cold frames are easy to construct, take very little care, and can provide you with fresh vegetables throughout the fall, winter and spring seasons. In fact, with the use of a cold frame it is possible to have fresh vegetables from your own garden all 12 months of the year.
HOT BEDS - if you want to go one step further, you can turn your cold frame into a hot bed by simply submerging a heating cable into the soil in your cold frame. Actually, a light globe, lit on a cool night will even help to provide warmth to your winter crops. The heating cable will also be of great value in helping root winter cuttings or start new seedlings. Of course, the heat will also help bring the winter vegetable crops to maturity quicker. But, I am getting ahead of myself, let's first talk about how easy it is to build a cold frame:
MATERIAL FOR A COLD FRAME - you don't have to be a carpenter in order to construct a cold frame. Even I can do it! There's a good possibility that you might have the materials on hand, or you can easily obtain them from a salvage yard.
The size doesn't make any difference. Start with an old window sash or aluminum/glass doorframe, then build the box to those dimension's. For example, if the window sash is 36 inches wide and 6 feet long, that's the size you want to make the frame. If the sash does not have glass in it, you can replace the glass with fiberglass, polyethylene or a similar material.
It's best to use sturdy 2 by 6's, 2 by 8's, or 2 by 10's to construct the sides of the cold frame. It's up to you, you can use new wood or to keep costs down by using what you have on hand or second grade lumber.
PLACEMENT OF THE COLD FRAME - if possible the cold frame should face south for the maximum sunlight exposure and it should have at least a 10 percent angle for added sunlight exposure.
If a southern exposure is not available the second choice would be a western exposure. Third choice would be an eastern exposure and the least desirable would be a northern exposure. When possible select a site with a slight forward facing slope, for better drainage.
BUILDING A COLD FRAME - you can either set the cold frame on top of the ground or bury it in the ground. You will find you will get better insulation if it is at least partly below ground level
If the cold frame faces south, build the cold frame so it is higher in the back (the north side) and lower in the front (the south side). Ideal dimensions would be approximately 18 inches at the back and 12 at the front. This provides a good angle for sun exposure and a slope for excessive rain to drain off.
Put the sash on top of this frame, holding it in place with hinges on the high end, the north side.
SOIL PREPARATION FOR PLANTING - prepare the soil to a depth of 12 to 18 inches. Mixing compost, processed manure, peat moss or other forms of organic humus with your existing soil to create a good fertile soil. Or, if your soil is quite poor you may want to start with a premixed commercial planting soil. You probably will find it necessary to renew the soil every year or two.
COLD WEATHER PROTECTION - if winter weather gets exceptionally cold, say down into the low twenties or teens, you will need to cover the cold frame with old burlap bags, old blankets, or any type of cloth material to provide added protection during the cold spell. Then once the weather has subsided, the covering material should be removed. Of course, if you have added a heating cable that will help some, but probably not enough heat to save your vegetables, so covering during really cold weather is still a good idea.
WARM WEATHER CARE - on a warm sunny day, during the fall, winter or early spring it will be necessary to open the window sash for ventilation. You can use a stick or wedge, or any similar material to prop it open. Also, during the warmer early fall and early spring months it may get too hot, making it necessary to cover the window sash with a shade cloth, or by treating the glass with a lime wash, to provide additional shade and cooler temperatures for your plants.
WATERING PLANTS IN A COLD FRAME - you will have to experiment a little to determine how frequently to water your cold frame because the watering requirements will vary from day to day and season to season. Generally, during the winter season the cold frame will only need to be watered once a week. Or you can let Mother Nature do the job by opening the top of your cold frame on a rainy day.
FERTILIZING - if the soil is prepared properly, there should be little or no need for feeding during the winter. The exception may be leaf crops, like lettuce, spinach and chard. A light feeding of an organic type 'Vegetable Garden' fertilizer two or three weeks after planting would be beneficial.
SLUGS - the warmth of the cold frame may attract slugs, so be on the lookout for them and take appropriate steps to keep them under control should they become a problem.
BEST VEGETABLES TO GROW IN YOUR COLD FRAME - leaf lettuce is undoubtedly the best crop to grow. It grows rapidly and abundantly in a cold frame. And, there's nothing like fresh, nutritious greens, picked from your own garden during cold winter weather. Spinach is also an excellent green to grow. Other crops that grow exceptional well in cold frames or hot beds are green onions, radishes, and chard, round or little finger carrots, endive and other greens. As you become more familiar with using your cold frame/hot bed, you will undoubtedly want experiment with other vegetables as well.
In addition to growing vegetables, a cold frame is an excellent place to start new seeds in springtime or to take cuttings in the fall and winter months of your favorite evergreen plants. In fact, the propagation of new plants, including rhododendrons, camellias, azaleas and other broad-leafed and conifer evergreens, can take place in a cold frame. The cuttings can be taken any time from September until early February. You will find the cuttings will root better with bottom heat from a submerged heating cable.
If you want to cut costs this winter and grow some of your own produce, now would be an excellent time to build your own cold frame or hot bed. If you don't feel up to the challenge of building your own cold frame, specialty firms (like Charley's Greenhouses & Garden Supplies) offer nice looking, pre-made insulated cold frames.