Raised bed gardens can be converted into multi-season greenhouses. Some people claim you can grow vegetables all winter long in a covered raised bed garden.
Winter Raised Bed Gardens
I have to admit, I breathe a sigh of relief in late October and early November. The vegetable garden looks bare outside my kitchen window but the lack of plants means less work. Less watering, less weeding. Cold weather also means fewer trips around the paths with the push mower or the weed whacker.
There are a few chores left for me to do. I need to drain and store the hoses. The tomato cages I’ve taken apart and stacked next to the shed need to be stored upon the hooks Hubby added to the shed walls. The asparagus, looking dismal and forlorn during these cold rainy days, should be cut back, and the strawberry plants covered with pine straw.
Looking at my raised beds, it’s a shame that all that space goes to waste during the winter months. From now through early March, my beds remain idle, four months of time in which my prudent and frugal nature cringes. I want something green. I want something edible.
I want to grow a winter raised bed garden.
Converting Raised Beds to Cold Frames
The first option, if I do choose to use the raised beds for another crop this year, is to convert the existing raised beds into cold frames. Raised garden beds easily convert into cold frames using covers made from old glass windows, plexiglass, or wooden frames inset with glass.
The angle of the top frame is important. It maximizes sunlight and warmth and prevents the plants inside from getting too hot. An angle of 15 degrees to 55 degrees works well to capture sunlight and warmth. The greater the angle degree, the more sunlight is captured inside the cold frame.
Another option for converting raised beds to winter growing environments is through the use of PVC-pipe hoop houses. A hoop house is a long tunnel made from bent PVC pipe affixed to wooden braces. Plastic stapled over the tunnel forms it into a greenhouse. This article includes pictures and instructions to build a PVC greenhouse or hoop house. I really want to give it a try and I already have PVC pipes in the garage from my failed pea trellis idea. Might as well use them for something else!
Warmth, Light, Water
Plants growing in my garden zone (6b or 7a, depending on the year) need warmth, light, and water to thrive during the winter months. Don’t expect to grow tomatoes, peppers or eggplants; try lettuce, beets, turnips, mustard greens, and other cold-hardy vegetables instead.
I find that water is actually the hardest thing to get to my plants the few times I’ve grown plants outside in a cold frame during the winter months. Without the hose nearby, I’ve got to carry water to the cold frame, and frankly when it’s 30 degrees out and there are ice patches on the lawn I’ve rather be curled up by the fireplace with a good book. But plants do need water during the winter, so figure on a way to either crack open the top of a cold frame (easy to do if you use old storm windows or a similar device) to allow rain to reach the soil or another way to water plants inside a hoop house or PVC greenhouse.
Insulation for Plants – Mulch
Another way to keep plants warm is through the use of mulch. Shredded leaves or fallen pine needles, also called pine straw, provides plenty of protection for many cold-weather crops. Spread the mulch across the top of the soil in a thick layer around winter-hardy plants.
Will I make my PVC greenhouse this year? Probably not. But I am tempted to plant lettuce seeds and I think I will this weekend. I might as well try it. I have cold-tolerant varieties stored in my seed box waiting for next spring. It certainly won’t hurt to plant them and haul one of the old gymnasium windows our friend saved for us from a refurbishing project he completed on a school gym in Richmond. It’s good to have friends who save big, heavy windows – in frames, no less – for your garden projects!
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Jeanne Grunert is a certified Virginia Master Gardener and the author of several gardening books. Her garden articles, photographs, and interviews have been featured in The Herb Companion, Virginia Gardener, and Cultivate, the magazine of the National Farm Bureau. She is the founder of The Christian Herbalists group and a popular local lecturer on culinary herbs and herbs for health, raised bed gardening, and horticulture therapy.