How to use cover crops in a home garden
Cover crops are a useful (and inexpensive!) way for vegetable gardeners to manage weeds, improve the soil, and help control erosion. Not intended for harvest, cover crops are planted either before or after the harvest of a vegetable crop, or in fallow gardens. Many gardeners think cover crops only have a place on large farms, but even if you grow in a small vegetable patch or raised beds, cover crops can prove very helpful.
Typically planted in the autumn or spring, cover crops are left to grow and then mowed down and/or turned into the soil before the vegetable garden is planted.
Cover crops provide many benefits. Which exact benefits are achieved depends on the species of cover crop used. Some possible benefits include not just those mentioned above, but also the creation of habitat for various species of pest-eating beneficial insects and an increase in overall garden biodiversity.
There are dozens of different cover crops available to farmers, but not all of them are appropriate for home gardens. Seeking appropriate cover crops for the home garden requires careful thought. Some can become invasive if they can’t be turned under deeply enough. Others may reseed prolifically if they aren’t mowed at the exact appropriate time, causing a “weed” issue in the garden. That being said, there are a handful of cover crops that are excellent choices for the home vegetable garden.
Decide which to plant
First, before deciding which cover crops to use, it’s important to understand that cover crops are typically divided into two categories: Warm-season cover crops and cool-season cover crops.
• Warm-season varieties are planted in the spring or summer, either before a vegetable crop or in place of one in a fallow area of the garden.
• Cool-season varieties are planted in the late summer or early fall, after your veggies have been harvested. They must be planted early enough to germinate and grow before winter arrives. Some cool-season cover crops survive the winter and re-grow in the spring while others are killed by freezing temperatures.
Some of the best warm-season cover crops for home gardens include annual buckwheat (Fagopyron esculentum) and cow peas (Vigna unguiculata). The best cool-season cover crops include oats (Avena sativa) and winter rye (Secale cereale).
If you’re new to cover cropping and a little nervous about getting started, I recommend oats because they are winter-killed here in Pennsylvania. If you sow them in the late summer or early fall, they’ll most likely die over the winter. You can simply leave their residue in place and plant right through it the following spring. No need to till them under; just trample them flat against the ground. A layer of dead oat plants serves as excellent weed control.
Tips to remember
Here are some tips for using cover crops in a home garden. Be careful to follow them as they’ll keep the cover crops from becoming potentially invasive.
1. Distribute cool-season cover crop seed over the garden soil toward the end of the growing season. Warm-season cover crop seeds should be sown in the early spring. There’s no need to cover the seeds of cover crops with soil when planting.
2. Only allow the cover crop to grow until it reaches the flowering stage. Mow or cut down the cover crop just as it comes into flower and leave the trimmings lie in the garden.
3. If you mow too early in the plant’s development, it will regrow and try to bloom again, so wait until the cover crop begins to flower to mow or cut it down as close to the ground as possible.
4. After mowing your cover crop down, it’s time to consider whether or not you should till the debris into the soil. Tilling is very destructive to soil life, but for some cover crops, tilling them under is the best way to ensure they’re killed and won’t resprout. Tilling also incorporates the cover crop residue into the soil where it can decompose and release nutrients to the soil faster, and add food for soil microbes further down in the soil profile.
5. For winter-hardy cover crops that are not killed by a properly timed spring mowing, tilling may be your best option. But, for cover crops that are readily killed by either cold temperatures or an aggressive mowing timed just as the plants come into flower, there’s really no need to turn the debris into the soil.
6. With all cover crops, whether or not you choose to till them in, wait between two and four weeks to plant vegetables after the crops have been mowed or turned into the soil. This mow/wait/plant cycle is very important as it allows some of the crop residue to breakdown before the vegetable crop is planted. Cover crop residue in a fresh state stimulates a flurry of microbial activity that can be detrimental to plant growth. Wait a few weeks prior to planting to allow this flush of activity to slow.
Consider adding cover crops to your vegetable gardening schedule. The benefits are many.
Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden,” “Good Bug, Bad Bug,” and her newest title, “Container Gardening Complete.” Her website is jessicawalliser.com. Send your gardening or landscaping questions to [email protected] or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.