Fall Gardening: What are Cover Crops?

If you plant green manure this fall, your garden will work harder for you next year, guaranteed. Cover crops, also called green manure, are the hardest working plants in the garden. You might think cover crops are used just for farm land and large growers, but the benefits are the same whether you have acres of farmland or a small vegetable garden in the back yard. It’s not too late to plant cover crops now in Philadelphia and all of the Northeast and Zone 6, and Philadelphia’s Burpee Seed Co. has all the cover crop seeds you’ll need.

The benefit of growing organic winter cover crops is to improve the garden soil during the months when the garden is down. Green manure suppresses weeds, amends soil, increases organic matter, adds organic nitrogen production, prevents soil erosion,and controls pests and disease, making your garden productive and healthier for the next growing season. It is used to manage a range of soil macronutrients and micronutrients.(1) It also increases worm and microbial activity and provides aesthetic value and color in the vegetable garden during the winter.(2)

View slideshow: Cover Crop

Green manure crops include legumes such as cowpeas, soybeans, annual sweet clover, vetch, sesbania, and velvet beans, as well as non-leguminous crops such as sudangrass, millet, sorghum, and buckwheat. Legumes are often used for their nitrogen adding abilities, while non-leguminous crops are used primarily for weed suppression and addition of biomass to the soil.

The easiest cover crops to grow are:

Cereal Rye - Rye is available in two different types: annual rye and cereal rye. Plant cereal rye in early fall, and it will grow until late in fall and resume growing in spring. Cereal rye, are very cold-tolerant.
Annual Rye - With annual rye, which winterkills in Zones 5 and colder, you'll be able to plant your garden earlier, since you won't have to turn the cover crop into the soil in the spring.
Field Peas -This dynamic duo combines the benefits of a legume (peas) that fixes nitrogen and a grain. Field peas are cold-tolerant
Oats - Oats contributes plenty of organic matter and are also cold-tolerant.
Buckwheat - Buckwheat is very fast-growing broadleaf plant that provides a quick canopy to shade weeds. Don’t let it go to seed, or you'll have buckwheat growing in your garden.
Clover - Clover comes in many sizes and shapes. It builds rich soil and helps to fix nitrogen. White Dutch clover works like living mulch because it tolerates both shade and traffic. Yellow sweet clover is an excellent soil amender and helps build good soil structure. Crimson clover does as well, and looks great too.(3)

If you decide to plant cover crops in the fall, be sure to allow them plenty of time to become established. This means planting them four weeks before a killing frost, meaning right now in the Philadelphia region. Planting cover crops are as easy as planting grass seed. Gently work the garden soil with a rake, spread the seed over the soil, rake into the soil, then water. Be sure to water if there’s not much rain.

Burpee Seed sells all the cover crop you need. It’s not too late; here’s what’s available through Burpee Seed Company right now. Click highlighted links for more information:

Cover Crop, Cold Climate Mix is a fall cover crop specially blended for northern climates.Contains of 70% Winter Grain Rye, 30% Hairy Vetch. Excellent northern combination for increasing organic matter content in the garden, erosion control, Nitrogen Fixation and improving water, root and air penetration in the soil.
Cover Crop, Hairy Vetch is a fall cover crop fixes soil and blooms with flowers. Hairy Vetch and Nitrogen fixing legume providing excellent biomass over the winter, erosion control and ground cover, blooms with pretty violet flowers.
Cover Crop, Warm Climate is a fall cover crop specially blended for warm climate winters. Organic cover crop that will be very successful in warmer climates contains of 70 % Winter Grain Rye, 30% Field (Austrian) winter Pea. Warm climate is a mix of rapid growing winter rye for erosion control and weed suppression plus Austrian winter pea for Nitrogen fixation and aesthetic color during the winter.
Cover Crop, Winter Rye is a fall planted cover crop helps the soil, and looks great all winter. Winter Rye is the most popular winter cover crop because it provides rapid growth of green plants that choke out weeds, provides organic matter to the soil, and prevents erosion.

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The important thing is to destroy your cover crops before they set seed. Green manure crops are grown for a specific period, and then plowed under before reaching full maturity in order to improve soil fertility and quality. The best time to kill them is at flowering or when the seed heads emerge on grains. The annuals can all be killed at this point by cutting at the base of the plant. Wait 24-28 hours until the leaves and stems dry down, and then dig them in, it won't be long before the vegetation begins to decompose. After turning under a cover crop of grasses, wait two to three weeks before planting vegetables or flowers.

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