How to Grow Vegetables in Winter
Growing vegetables in the middle of winter can be a difficult task, but with the right precautions, it is possible to keep several hearty vegetables warm enough to survive the cold temperatures. Regardless of the methods you use, you should aim to keep your winter vegetables growing for as long as possible. Cool temperatures, especially at night, allow these vegetables to develop more sugar since they need the sugar to survive the low temperatures. These natural sugars improve the flavor of the vegetables.
Pick the right crops. You should always choose hardy, cold-resistant vegetables to use for winter gardening, but even amongst these vegetables, some hold up better in severe freezes than others. You should thoroughly research the minimum temperature and growth requirements for a winter vegetable before committing to growing it.
- Popular winter vegetables include arugula, beets, broccoli, Brussels sprouts, cabbage, carrots, cauliflower, chard, endive, favas, kale, garlic, leeks, lettuce, mustard, onions, parsnip, radicchio, and spinach.
- Onions are amongst the most resilient vegetables, with most types surviving temperatures of 0 degrees Fahrenheit (-18 degrees Celsius). The Walla Walla sweet onion is possibly the most resilient, with some reports suggesting that it can withstand freezes as low as -10 degrees Fahrenheit (-24 degrees Celsius).
- Brussels sprouts are also fairly resistant, and are able to last through temperatures as low as 3 degrees Fahrenheit (-16 degrees Celsius). Similarly, radicchio and endive both survive in temperatures as low as 5 degrees Fahrenheit (-15 degrees Celsius).
- Lettuce is one of the least resilient cold-resistant vegetables, but even it has been known to last in temperatures as low as 24 degrees Fahrenheit (-4 degrees Celsius).
Rotate the vegetables. Regardless of where you plant your winter vegetables, you should rotate the vegetables you plant from year to year. Planting the same crop in the same location will cause the soil to lose nutrients. Pests that are attracted to that type of vegetable will also be more likely to gravitate toward that location, causing damage.
- If you do not rotate the winter vegetables you plant in a plot, you should at least plant a different vegetable during another season, like spring and summer, to improve the quality of the soil.
Make use of walls. The outer walls of houses, sheds, and garage provide plenty of natural protection against harsh winter winds. If you live in a region that experiences mild to moderate winters, you might be able to get away using no further protection than a south-facing wall. South-facing walls allow the plants to receive maximum sunlight while protecting them from the majority of cold winds.
Use cloches. Cloches are, in a sense, portable green houses. They can be made from a variety of clear materials so that the wind is blocked from the plant while the sunlight is allowed to pass through. There are several designs that you can try.
- Hammer stiff metal spikes into the ground and prop glass panes over them in a triangular “teepee” style.
Cut the bottom from a clear gallon (4 liter) glass or plastic container and place the container over a smaller crop.
Build a polytunnel, also known as a PVC hoop house or high tunnel. These are basically the same thing as a cloche, except on a larger scale.
- You will need to insert several large, half-hoops of PVC piping or electrical conduit into the ground around over the length of the plant bed. These half-hoops should be large enough to allow a person to walk beneath them, about 5 feet (2 m) across, 5 feet (1.5 m) tall, and spaced 5 feet (1.5 m) apart.
It may be best to nail the hoop frames down to heavy wood boards to provide them with extra support.
Hook clear plastic sheets or sheer poly fabric over the frames. You can nail the sheets in place, or you can weigh them down with heavy rocks or sandbags.
Construct a cold frame. A cold frame is a more permanent structure that can be used from year to year. While you can build one from wood and fiberglass, you can also buy one pre-built online or from a garden supply store. A cold frame is about 18 inches (46 cm) in the back and 12 inches (30 cm) in the front, with a clear, slanted roof that gathers the sun’s warmth from an angle.
Grow your vegetables in raised beds. Raised beds use stones, bricks, or wood to create frames around the vegetable plot. These frames are then filled with nutrient-rich soil. By keeping your winter vegetables elevated, you can keep the soil warmer than ground soil by a difference of 8 to 12 degrees Fahrenheit (11 to 13 degrees Celsius).
Cover your crops. Ground coverings insulate the soil, keeping it warmer overall than it would be if exposed directly to the brisk winds of winter.
- Use soil to keep your root vegetables covered. Pile the soil around the shoulders of your root vegetables, like carrots, but do not cover the leaves that sprout above ground. The leaves need to absorb sunlight, but keeping the root vegetable itself covered is often a sufficient way to protect these crops against frost.
Warm things up with mulch. A coating of mulch should be applied to the crops just before the ground freezes. In extremely cold regions, the layer may need to be as deep as 1 foot (30.5 cm), but it can be a bit lighter in warmer regions with less severe temperatures. For best results, use light mulch, like stray, pine needles, shredded leaves, or grass clippings. You can even get as heavy as light bark mulch, especially in colder regions. Make sure that you do not pile the mulch over the sprouting leaves. Otherwise, you may inadvertently kill the crops by depriving them of sunlight.
Plant vegetables indoors. You can grow many vegetables during the winter in your home, provided you have enough space and the proper resources. Most vegetables have deep root systems and need to be planted in containers with considerable depth. Frequent watering is often necessary, depending on the specific vegetable you choose to grow, and you may need to supplement natural light with artificial grow lights if the gray winter skies do not let much light in through your windows.
- Find out when, on average, the first killing frost occurs. Some vegetables can thrive in the light to moderate freezes of fall, but not in the severe freezes of early to mid winter. Knowing when killing frosts occur, along with which cool weather plants cannot survive them, can help you calculate how late you can plant those cold weather plants without risking damage to the crop.