by Deb Bigelow, Master Gardener volunteer, and Colleen Cavagna, Community/Consumer Horticulture Educator with Allegany County Cornell Cooperative Extension
Now that cover crop seed is widely available in small quantities for home gardeners, it’s easier than ever to incorporate these wonder-workers into your garden plans.
Cover crops are helpful for beds that are too weedy to give good yields or that need organic matter. They can also attract pollinators and slow erosion.
You might think of farms when you think of cover crops, but they can work in any size area. Many cover crops need to be tilled into the soil, so if you can’t turn the cover crop under, that might limit your use of cover crops.
While planning your seed purchases, consider buying seeds for a cover crop. A feed store that sells farm seed in bulk can sell a few pounds of their cover crop choice to a home gardener. You can also find seeds online.
You can plant oats as soon as the soil can be worked; that is, when the soil is not frozen, is not too wet and is warmed somewhat. To test your soil, dig down around four inches and try to form a ball with the soil. If you can form a ball that does not break apart in your hand, the soil is not ready— it’s too wet. Wait several days and try again, especially after additional rain. If you can form a ball that does not hold its shape in your hand, but crumbles apart with slight pressure, it’s time to plant.
Oats germinate readily in cooler soil, can tolerate wetness fairly well and, planted densely, can quickly cover the soil and prevent weed germination.
Oats tolerate a wide pH range but do require lots of sun.
Cut or mow at around 45 days of growth to kill the oats plants. (You won’t get a crop of oats; it takes 105 – 120 days for the oats to mature.)
You can let the dead plants dry on the surface. Just plant your vegetables or whatever it is you want to grow in between the dead oats. The dead oats will act as mulch. Oats are a “mulch-in-place” crop.
You can also till under the oats to add organic matter to the soil.
Plant oats again in early fall to make a winter-killed mulch that protects and conserves soil.
Another inexpensive, easy springtime weed suppressor is annual rye, which is a kind of grass. Don’t confuse annual rye with cereal rye.
Annual rye germinates easily in cool soils, and if planted thickly, it grows rapidly to a dense canopy that crowds out weeds. It can be cut several times and fed to pet rabbits or to chickens. Then till it under to decompose and add organic matter to your soil.
If you don’t have a mechanical means to turn the annual rye under, choose a different cover crop. Annual rye can become a real headache for a muscle-powered gardener!
Later in spring, after your soil is warmed to at least 50 degrees, you can plant buckwheat, the garden workhorse.
Not only does buckwheat suppress weeds and gather up phosphorus for your subsequent crops, but the flowers will make your resident bees very happy.
Buckwheat requires cutting just after flowering, unless you want to save seed or risk lots of volunteers (not a really bad thing) the following year. Cut buckwheat approximately 2-3 inches up from the soil surface to stop growth. You may then just lay the stalks on the surface to dry and mulch your next crop.
Although buckwheat does need warmer soil to germinate than oats or rye, meaning it probably can’t be planted in our area much before early June, it grows so fast that fall-planted crops can be easily accommodated when the buckwheat has been cut (killed) at flowering.
If you want to grow buckwheat so you can get seed you can eat, you would probably have to forgo getting another crop in that space before frost.
More information on cover crops
For comprehensive cover crop information see the Sustainable Agriculture Research and Education website.
For more information, in Allegany County, call your Cornell Cooperative Extension Master Gardener Volunteers at (585) 268-7644, ext. 23. In other counties, see contact information for your local Cornell Cooperative Extension office here.
Weeds that cover crops can’t defeat
There are some troublesome weeds that cover crops can’t compete with.
One is lesser celadine. It is an early spring ephemeral, starting to grow and develop reproductive structures in cool and wet conditions. It also reproduces through tuberous roots that can be deep in the ground and remain after the plant dies back. A cover crop that competes with it must be able to thrive under the same conditions, and these cover crops can’t.
In addition, seeding a crop into the infested area means disturbing the soil, which will actually help the invader reproduce.
Bishop’s weed is another invasive plant that cover crops can’t conquer. This weed does best in damp shade, and cover crops generally need sun.
For bishop’s weed, it’s best to cut the foliage repeatedly over several seasons’ time, thereby depleting the plant’s energy reserves enough to kill it. It’s not an easy remedy, I know.
If the area is not huge, you can cover the area with cardboard in several layers and weight the cardboard down to deprive the plant of light. If you don’t weight the cardboard down, the plant will slowly lift the cardboard.
I have seen people put thick clear plastic over these areas to cause a heating effect that roasts the plants. The plastic must be weighted down as well.