Home & Garden Garden A Regional Guide to Cover Crops to Banish the Bare Ground By Tom Oder Writer Furman University. Tom Oder is a writer, editor, and communication expert who specializes in sustainability and the environment with a sweet spot for urban agriculture. our editorial process Twitter Twitter Tom Oder Updated March 09, 2018 Rapeseed. Strangeways70/Shutterstock Share Twitter Pinterest Email Home & Garden Planting Guides Indoor Gardening Urban Farms Insects There are varieties of cover crops for every season that home gardeners can use to enrich soil, hold down weeds and grow better veggies. "No bare ground!" would make a good battle cry for a growing legion of backyard farmers. They could shout it when lettuce bolts in the spring and needs to be pulled out but the ground’s not warm enough to plant summer crops. Or when summer crops wilt early in the heat of late July and August and should be removed but there’s not enough time before fall to plant a new crop and reap a second harvest. "The idea is to always have something growing," says Andy Clark, communications director for the Sustainable Agriculture Research and Education program (SARE), an organization in the USDA’s National Institute of Food and Agriculture, and a community gardener for 30 years. SARE was established to help farmers become more profitable by awarding grants to promote environmentally friendly agriculture. Its findings, though, are beneficial to home growers as well. For instance, that "something" Clark referred to for home growers is a cover crop. Cover Crops Can Work the Soil in Winter "Winter is really the best and most likely time for the home gardener to use a cover crop," Clark said. "Why leave the ground bare all winter when you could have cover crops working on the soil for you?" Cover crops, though, can be used in any season and in any part of the country. As an example, Clark singled out buckwheat (pictured in flower above). "It is the cover crop of choice for much of the country following lettuce or other early spring crops," he said. "It is often the summer cover crop of choice, as well." The reason buckwheat works so well in instances where the goal is more of a rotation crop than a cover crop, Clark said, is because it only needs a short window of four-six weeks to sprout and grow. All of the other choices for summer cover crops require more time to grow and be effective. Citing two examples, he said sudangrass and cowpeas require a minimum of three months or more. Cover Crops Hold Down Weeds and Nourish Soil "If you don't plant cover crops," Clark cautioned, "you'll just have weeds." Cover crops not only hold down weeds, they provide many other benefits to the soil. They enhance the availability of nutrients such as nitrogen, add moisture to the soil, control erosion, help to control pests and, when turned into the soil, add natural biomass that helps to break up thick soils such as clay. All of these benefits result in increased vegetable yields for the home gardener. To reap those benefits, Clark says home gardeners should have a basic understanding of cover crops and then create a plan to use them. The two lists below will help home gardeners accomplish both goals. They are condensed from a SARE book, "Managing Cover Crops Profitably," for which Clark served as the project manager and editor. One list provides the names of the most commonly used cover crops for the fall, spring and summer growing seasons. The other offers a brief description of the primary benefits of each cover crop. All of the cover crops listed below are sown by seed, inexpensive and available from organic gardening sources, some nurseries and from online suppliers. Commonly Used Cover Crops Here are some examples of readily available and inexpensive cover crops. They are listed under the categories of legumes and non-legumes and the seasons in which they are typically used in different regions of the country. Southeast Fall – Legumes: berseem, crimson clover (pictured right), hairy vetch, subterranean clover, winter peas; Non-legumes: oats, rapeseed, rye (grain), wheat Early spring – Legumes: berseem, red clover, sweet clover, winter peas; Non-legumes: rapeseed, spring oats Summer – Legumes: cowpeas; Non-legumes: buckwheat, sorghum-sudangrass Mid-Atlantic Fall – Legumes: crimson clover, hairy vetch, subterranean clover, winter peas; Non-legumes: oats, rapeseed, rye (grain), wheat, barley Early spring – Legumes: berseem, red clover, sweet clover, winter peas; Non-legumes: rapeseed, spring oats Summer – Legumes: cowpeas; Non-legumes: buckwheat, sorghum-sudangrass Northeast Fall – Legumes: hairy vetch, subterranean clover; Non-legumes: oats, rapeseed, forage radish Early spring – Legumes: berseem, red clover, sweet clover; Non-legumes: rapeseed, spring oats Summer – Non-legumes: buckwheat, sorghum-sudangrass Upper Midwest Fall – Legumes: berseem, crimson clover, hairy vetch, medics, white clover, winter peas; Non-legumes: rapeseed, rye (grain), wheat, barley, forage radish Early spring – Legumes: berseem, medics, red clover, sweet clover, white clover; Non-legumes: barley, rapeseed, spring oats Summer – Non-legumes: buckwheat, sorghum-sudangrass Southwest Fall – Legumes: crimson clover, medics, subterranean clover Early spring – Non-legume: barley Summer – Non-legume: Sorghum-sudangrass California Fall – Legumes: berseem, lana woolypod vetch, medics, winter peas; Non-legume: rye (grain) Early spring – Legumes: berseem, sweet clover, white clover; Non-legume: barley Summer – Legume: cowpeas; Non-legume: sorghum-sudangrass Pacific Northwest Fall – Legumes: berseem, crimson clover, hairy vetch, lana woolypod vetch, medics, subterranean clover; Non-legume: rye (grain), wheat Early spring – Legumes: berseem, sweet clover, white clover; Non-legume: barley Summer – Non-legumes: mustards, sorghum-sudangrass grass Here are the primary benefits of the cover crops listed above. Legumes Legumes include a wide variety of familiar plants such as beans, peas and clovers. They are valued as cover crops because they transfer nitrogen from the atmosphere to the soil for use by subsequent crops, reduce or prevent erosion, produce biomass that adds organic matter to the soil and attract beneficial insects. In colder climates, winter annual legumes can be grown in the summer. Berseem Clover A fast grower that suppresses weeds, prevents erosion and is a heavy nitrogen producer that provides green manure that nourishes the soil when cut down. Can be grown as a winter or summer annual depending on the region of the country where it is used, but is the least winter hardy of all true annual clovers. Also known as Egyptian clover. Clover (Crimson) A popular choice for use in short rotations because of its rapid and robust growth habit. It is valued as a weed-suppressing green manure that has the ability to transfer nitrogen from the air to the soil and act as a soil builder. An added benefit is that it attracts bees, which play an important role as pollinators. Can be grown as a winter or summer annual. Clover (Red) A cover crop workhorse that is hardy in much of the United States (USDA Zone 4 and above). It loosens the soil, supplies nitrogen to the soil, acts as a soil builder and weed suppressor and attracts pollinating insects. It is very versatile in that it can be grown as a short-lived perennial, biennial or winter annual. It is also known as medium red clover and mammoth clover. Clover (Sweet) Sweet clover thrives in temperate regions that have mild summers. The annual varieties work best in the Deep South, from Texas to Georgia. Because sweet clovers have a strong taproot with branches that grow deep into the soil, they are valued for their ability to aerate the soil. They also are drought-tolerant, produce abundant biomass, moderate amounts of nitrogen and extract micronutrients such as phosphorus and potassium from the soil and release it in a form that would otherwise be unavailable to crops. Grow as a biennial, summer annual or winter annual. Clover (Subterranean) Subterranean clovers generally grow close to the ground, and most cultivars require at least 12 inches of rain during their growing season. They provide nitrogen to the soil and are excellent in loosening hard soils, controlling weeds and erosion. These clovers are cool season annuals. They are also known as subclover. Clover (White) These clovers can be planted between rows of vegetables where, once established, their tough stems can easily tolerate foot traffic. Used in this way, they become a living mulch that protects soil from erosion and suppresses weeds. An added benefit is they attract beneficial insects. They thrive under cool, moist conditions and shade. Also known as Dutch White, New Zealand White and Ladino. Cowpeas Considered the most productive heat-adapted legume in the United States. The densely growing foliage suppresses weeds, provides nitrogen to the soil and helps build the soil when it is turned under. Grow as a summer annual. Also known as Southern peas, black-eye peas and crowder peas. Field Peas Supply large amounts of nitrogen and serve as short-term soil conditioners when the foliage is turned into the soil. Can be grown as a winter or summer annual. Field peas are also known as Austrian winter peas (black peas) and Canadian field peas (spring peas). Hairy Vetch Considered a top nitrogen contributor because of its ability to make vigorous roots that supply nitrogen deep into the soil. Also serves as a weed suppressor, a topsoil conditioner and erosion controller. Winter hardy to USDA Zones 3 and 4, it can be grown as a winter or summer annual. Medics Medics have few peers in portions of California and the Plains because of their ability to tolerate dry conditions while providing nitrogen to the soil. In wetter areas, they can produce almost as much biomass as clovers. They also suppress weeds and help prevent erosion. Grow as winter or summer annuals. Medics are also known as black medic, burr (or bur) medic and bur clover. Woolpod Vetch This is a specialty vetch that is a faster-growing alternative to hairy vetch. It can be grown in USDA Zone 7 and warmer where it requires little or no irrigation as a winter cover, dependably provides abundant nitrogen and organic matter and is an excellent weed suppressor. Non-legumes Non-legumes include annual cereals such as rye, wheat, barley and oats, annual or perennial grasses such as ryegrass, warm-season grasses like sorghum-sudangrass and other plants such as mustards. They are valued as cover crops because they scavenge nutrients — especially nitrogen — left over from a previous crop, reduce or prevent erosion, produce large amounts of residue that add organic matter to the soil and suppress weeds. Commonly grown non-legume cover crops and their primary benefits are: Barley Marykit / Shutterstock This cereal grain is highly effective when used to fill in during crop rotations because it provides excellent weed suppression and can survive drought conditions. It also scavenges excess nutrients, adds organic matter to the soil and helps control erosion. It is a cool season (winter) annual. Buckwheat Because few cover crops establish as rapidly and as easily as buckwheat, it is considered the speedy short-season summer cover crop. Other attributes are that it suppresses weeds, provides nectar for beneficial insects, loosens topsoil and rejuvenates low-fertility soils. Grow as a summer or cool-season annual. Mustard Mustards have high a concentration of chemicals that are toxic to spoil-borne pests and some weeds. They also produce great biomass and scavenge the soil for nutrients. Oats An annual grass, oats provide a quick, weed-suppressing biomass. They have a fibrous root system that scavenges the soil to take up nutrients and can improve the productivity of legumes when planted in mixtures. Oats are a cool-season annual cereal grass that can reach four feet. They don’t grow well in hot, dry weather and are also known as spring oats. Radish Radishes have the distinctive capability to scavenge nitrogen from deep in the ground, break up compacted soil and suppress weeds. Rapeseed Valued because it is effective in controlling plant parasitic nematodes as well as weeds. Sow the seeds in either early spring or fall because the plants can withstand low temperatures. Rye (Grain) Rye is the most commonly planted cover crop in the United States. It is considered the hardiest of the cereals because it can be sown later in fall than other cover crops and still have time to establish an extensive root system that will prevent erosion and provide extensive nitrate leaching and exceptional weed suppression. Sorghum-sudangrass Hybrids Crosses between forage-type sorghums and sudangrass, these hybrids are unrivaled in their ability to add organic matter to poor or over-used soils. They love summer heat, grow tall and do it quickly, can smother weeds and suppress some nematode species. A "trick" to get them to grow deeper roots, which helps to break up compacted soil, is to trim them back when they get to about three feet. Grow as a summer annual. They are not frost tolerant. Also known as Sudex or Sudax. Wheat Best known as a cash crop, wheat can be grown as a cover crop. Used for this purpose, it prevents erosion, suppresses weeds, scavenges excess nutrients and adds organic matter to the soil. Grow as a winter annual.