ALBANY, Ore. – Need a summer cover crop? Farmers and home gardeners are finding buckwheat to be a good "green manure" during the warmer part of the year in Oregon.
A fast-growing summer cover crop, buckwheat is a succulent that can be grown as a green manure because it adds nutrients and organic matter to the soil. It also can smother weeds, protect the soil surface and provide habitat for pollinating and other beneficial insects, explained Dan McGrath, crops scientist with the Linn County office of the Oregon State University Extension Service.
Buckwheat seed can germinate within days of planting, especially if the soil is warmer than 55 degrees. Because it doesn't require much water and tolerates poor fertility, buckwheat succeeds in many less-than-ideal places in the garden. But it does not like shade or saturated soils.
Buckwheat improves the short-term tilth of the soil and prepares the garden bed for transplants. It is particularly efficient at taking up phosphorus from the soil and storing it in its tissues. Because it grows so fast, buckwheat is ideal for planting in places that might be left bare over the summer, such as spare garden beds whose spring crops are harvested and fall crops are yet to be planted.
"Sometimes home gardeners get overly ambitious with a rototiller in the spring," McGrath said. My advice to those gardeners is to plant buckwheat to hold the tilled area until there's time to plant new crops."
Buckwheat reaches flowering stage at about two to four feet high in about five weeks. It continues to flower for several weeks, then sets seed two to three weeks after flowering.
Can it become a weed?
"Under certain circumstances," McGrath said. "But, I consider it to be a 'good weed' because it is easy to kill and crowds out other weeds that are much more difficult." Home gardeners can easily pull it out or chop it down, McGrath added, before it sets seed. Since buckwheat is frost-sensitive, it will winter-kill naturally.
Plant buckwheat in the spring to early summer. Scatter the seed over the garden bed at a rate of about one pound per 500 square feet of garden space (about three ounces per 100 square feet) and rake and water in. Although buckwheat does not require much water, plants may appear wilted on hot summer afternoons.
Mow or cut down buckwheat within two weeks of first flowering if you want to avoid setting seed. When you turn the buckwheat plants or any cover crop into the soil, they begin to decompose. "It's not wise to plant into decomposing organic matter," McGrath warned. The fungi and bacteria decomposing the cover crop residue will attack the new plants' seeds and roots.
"Regardless of the cover crop, after incorporating it into the soil, wait a minimum of three weeks for it to decompose before planting a vegetable crop."
Buckwheat seed can be purchased from farm supply stores, garden centers, seed company websites and mail-order catalogs.