Ken Maki is a contributing writer for State-by-State Gardening magazines

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Space Saver Tips for Winter Vegetable Gardening
by Ken Maki    

This lean-to greenhouse houses container plantings with ease.

Like most gardeners in the South, you probably maintain a vegetable garden for three seasons: spring, summer and fall. But if you’re not living in Zone 9, where plants can grow all year round without much protection, you might think that keeping a winter garden is difficult at best.

Don’t be too quick to dismiss the possibility. With a bit of attention, most fall garden vegetables can survive long enough for a winter harvest. You can also grow a winter garden with the help of a cold frame, hot bed or a lean-to greenhouse. These do-it-yourself structures can provide ample protection for winter vegetables, and they don’t take up much room in your yard. 

Build A Cold Frame

Cover cold frames in cold weather for increased protection.

Strictly speaking, cold frames collect heat from sunlight and do not require any additional heat sources. If put in a sunny location, cold frames can produce a reliable source of cabbage, greens, broccoli, parsley, celery or turnips. While these vegetables can survive temperatures as low as 22º F on their own, a cold frame can provide extra protection down to 12 to 15º F.     

Cold frames are simple to build. The frame (or bed) can be made out of a variety of materials, but cinder blocks, concrete and treated wood (cypress) are the most popular. Whatever you choose, make sure you materials are able to withstand temperature extremes and resist decay. Do not choose materials that will harm your plants, such as wood treated with creosote or pentachlorophenol.

Size depends on need, but a four-by-six-feet cold frame should be large enough. You can go a bit bigger, but be sure the middle vegetables are within an arm’s reach from the perimeter the frame. Since the vegetables will be growing in tight quarters, you will probably have to care for them by reaching inside.     

A well-chosen cover is critical to success. I’ve seen some resourceful gardeners affix old storm windows to the frame with hinges. If you want to construct the frame anew, use fiberglass panels or sheets of plastic as the windows. It important that window component of the cover be clear, as to provide the plants with the necessary heat and light. It is also important that the closed cover provides enough for the tallest growing plants. If you can construct a dome structure out of bent wood and sheet plastic, vegetables can flourish.      

The cover should provide a good enough seal so as not to let in a cold night draft. You will have to open the cover frequently for plant care, so it’s important that it’s not too heavy. If you are growing cool-season crops, you should open the frame during warm periods, above 40º F, for ventilation. Direct sun on a warm winter day can raise the temperature inside to over 100º F, and the resulting high humidity is a haven for diseases like mildew.      

Unless you have experience with cold frames, I would not try to grow anything that requires pollination, like cucumbers or summer squash. 

Preparing The Soil

The better the soil mixture you use in the bed, the better the bounty. For best results with root crops, prepare the soil by double digging. Though this task is a lot of work, it will provide the benefits of better drainage and (as a result) a healthier root system.

When you’re double digging, amend the soil with good compost. On both the top and bottom level, add about one bag of topsoil per every 10 to 12 square-feet. Mix a bag of cow manure into the top layer. This provides essential nutrients and improves soil texture.   

Turn The Cold Frame Into A Hot Bed

If you’re still concerned about the perils of winter growing, you can transform your cold frame into a hot bed. By making room for a light bulb or two, you can add enough heat to melt snow or keep temperatures from falling to a critical level. With more money, you can fancy up a hot bed with a thermostat control, insulation and buried heat cables. These indulgences will provide the peace of mind of a climate-controlled environment.     

There is an organic alternative to the bells and whistles of a hot bed. Some cold-frame gardeners simply put fresh manure under the soil. As it composts, it provides the necessary heat. 

Lean-To Greenhouse

Lean-to greenhouse

You can also maintain a winter vegetable garden in a lean-to greenhouse. Unlike a freestanding greenhouse, this style simply leans against the east or south side of a building. In these structures, you can either grow your vegetables in the ground of a pre-existing flowerbed or in pots on a series of benches and shelves.

If you locate this structure off a patio door or around a window, you’ll have an easy way to pipe in the necessary heat. If you need more, use a small portable heater with a thermostat.

Make the frame of the lean-to out of PVC pipe, galvanized tubing, electrical conduit or wood. (Use a treated redwood lumber if the structure is permanent.) To prevent water damage, construct the roof of the lean-to out of fiberglass. Make the walls out of polyethylene plastic sheets, which can be attached to the frame with greenhouse clips or battings and staples.

If your structure is wider than four feet, you’ll want to add a door. A typical patio door will do, and it’s easy enough to install by yourself. If your structure is less than four feet wide, then you probably only need to include a retractable side panel (a plastic sheet that can be easily rolled up and down). Either a door or panel will provide the necessary ventilation.

A quality greenhouse can provide a good growing environment for vegetables throughout the winter, and it can even protect the true warm-season crops like tomatoes. Whether you’re using your lean-to as a place to over-night container plantings or raise ground-grown vegetables, the addition will pay for itself in nutrition in no time.

From State-by-State Gardening November/ December 2003. Photos courtesy of Ken Maki.


Posted: 12/05/12   RSS | Print


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