Garden Variety: With hardy crops and cold protection, gardeners can keep on growing

Freezing temperatures will likely arrive over the next few weeks in northeast Kansas, but the gardening season continues for vigilant gardeners who are interested in prolonging the harvest.

How do these gardeners keep vegetables growing into fall and winter? Only certain crops are suitable for it in this area, and some crops are hardier than others. Planting date also makes a difference. When freezing temperatures do arrive, frost protection materials or structures are essential to keep plants thriving.

Cool-season crops are ones that prefer the milder temperatures of spring and fall, in contrast to warm-season crops that thrive in the heat of summer. The best bets for fall and winter are leafy greens, cole crops and root crops such as carrots, radishes and turnips.

Fall crops should be sown in late July through mid-September depending on the maturity rate of the crop being planted. This gives time for plants to grow and establish roots prior to the arrival of freezing temperatures. If you planted a fall garden at that time, you should be set up to extend the season with frost protection in the coming weeks.

Warm-season crops such as peppers, squash and tomatoes may still be producing fruit right now, but they will fade quickly with colder temperatures, even with frost protection.

Frost protection materials and structures include mulch, floating row covers, low tunnels, cold frames, high tunnels (hoophouses), and greenhouses. Plastic sheeting and bed sheets or other large pieces of fabric could also be used as a substitute for floating row covers or to create a low tunnel.

Mulches such as straw, hay, chopped leaves or other plant materials can help to insulate the soil around the plant. Mulch is great for crops such as carrots, which are already protected in the ground and have a high tolerance for cold temperatures. Well-mulched carrots can often be harvested throughout the winter months, even without the use of additional cover. Mulch may be less desirable with leafy greens that are harvested close to the ground, however, as it can get mixed up with the crop.

Floating row covers are large pieces of lightweight fabric designed to protect plants from frost and pests. Air, water, and light pass through the row cover, allowing it to be left over the top of the plants for short periods of time. Secure the edges of the cover with pins, rocks, weights or other items to keep it from blowing away. Leave some slack in the cover to allow for plant growth. Floating row covers are also helpful in the spring and as a pest barrier for certain crops.

If using plastic sheeting, bedsheets or other materials as makeshift row covers, remove them during the days when temperatures are mild or warm to allow air, water and light to reach plants. With plastic especially, use caution on warm, sunny days to avoid overheating plants.

The next step up from simple row covers is to build a low tunnel, which is a covered frame over plants. Think of it as a miniature hoophouse over the crop. Use wood, wire or PVC pipe to build the frame and hang row cover or plastic over the top for protection. Again, the cover needs to be secured to keep it from blowing away.

Another option is to build a cold frame. This works best for crops planted in small square or rectangular groupings. The idea is to make a frame with lumber, blocks, straw bales, etc. around the plants that need protection, then place a clear cover over the top. Old windows are popular cold frame covers, but any sheet of clear glass, plastic or plexiglass is suitable. If the sides of the frame are tall, make the north side taller and the south side shorter so that plants get the full benefit of the afternoon sun.

The best season extenders are high tunnels (hoophouses) and greenhouses, but they require a significant investment. These are what commercial growers in the area use to extend their growing seasons into fall and produce vegetables earlier in the spring. If you’re interested in adding these structures to your garden, do some research to determine the best options for the site and intended crops.

Jennifer Smith works in regulatory horticulture and has worked as a horticulturist for various government entities. She has experience in landscape design and maintenance and as an educator.


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