Green Manures and Cover Crops: Plants That Give Back

by Brian LeDuc

Plant a Green Manure and give back to your soil! Often as the growing season slows and we have been enjoying the fruits of our labor, we forget to give back to the garden. Be proactive and increase soil fertility without promoting weed growth; plant a Green Manure!

'Green Manure' and 'Cover Crop': Two Interchangeable Terms

For years farmers have been rotating their crops and planting “Green Manures” or “Cover Crops” in their fallow (unused) fields.  Green Manures are plant varieties which help to replenish nutrients to the soil that your plants have absorbed and used to grow and produce fruits and flowers throughout the season.

These specialized, nutritional plants store or “fix” these nutrients into the soil, or themselves, and then are turned back into the garden early in the spring (using a shovel or tiller). Use of green manures can drastically reduce or even eliminate the need for fertilizers in the spring. But that’s not it! Other positive benefits of cover crops include:

  • Weed suppression. As cover crops establish themselves, they out-compete pesky weeds.
  • Creating habitat for pollinators and beneficial predatory insects.
  • Keeping the soil from becoming compacted or eroding. Wind and water can do enormous damage to unprotected ground in a short amount of time - green manures stabilize soils and protect against erosion.
  • Bio-accumulators / Dynamic accumulators. Some varieties have extremely deep roots, which tap into nutrients deep within the soil and bring them to the surface.
Hairy Vetch & White CloverHairy Vetch & White Clover
Hairy Vetch & White Clover

Which Plants Make The Best Green Manures?

Partridge PeaPartridge Pea
Partridge Pea

The list is extensive, but below are some of the better-known varieties.

The Legume Family is one of the most widely used Green Manures. Consisting of many different types of Clover, PeasVetch, and others, legumes contain symbiotic bacteria in their root systems, which help to fix nitrogen into the soil in a form that future plants can use.

You may have heard of using legumes in 'succession planting' - an idea that illustrates green manures in action. Because 'heavy feeder' crops like corn require nitrogen-rich soil to produce great-tasting ears, farmers and gardeners alike must figure out how to replace all of that nitrogen after each crop has been harvested. One simple answer is to plant beans or peas directly after corn - two well-known legumes that are infamous for leaving a slew of nitrogen in their wake. So, peas follow corn, which then gets planted again and is followed by peas (or clover, or beans), which then follow corn all over again - all in succession!

Other common green manures not in the Legume Family, including Rye, with its deep roots and hearty characteristics, great at withstanding colder temperatures and decreasing erosion, as well as buckwheat and sorghum.

Planting Green Manures Is Easy!

  1. Plant Early to Mid Fall to prepare for spring planting, or plant in early spring to prepare for Summer or Fall planting.
  2. Let your cover crops grow. Some hardier varieties will grow very slowly in colder temperatures, and then resume growth in the early spring. Others will die back after a hard frost (this is called 'winter kill').
  3. About 3-6 weeks before your new planting, mow down the cover crop before it goes to seed. Then till in to the soil to add organic matter and additional nutrients to the soil. 
  4. Always wait 3-6 weeks after tilling to plant your new crops to allow time for the nutrients to be released into the soil through decomposition.  Also, in the case of cover crops like Rye, the compounds which keep other seeds from germinating (one of its main benefits for weed reduction) will no longer be present to interfere with your new plans.
Canada Wild Rye GrassCanada Wild Rye Grass
Canada Wild Rye Grass

Find The Perfect Cover Crop

Green Manures/Cover Crops can be as simple or complex as you want to make them.  You can mix varieties and calculate the exact amount of max nitrogen output per square foot or just scatter some clover and have a beautiful green carpet.  Naturally give back to your garden and its habitat to keep it healthy and producing so you can continue to enjoy it for years to come!

For help choosing your cover crops, read these helpful articles!

Shop Cover Crop Seeds

  1. Soil Boost & Pollinator Seed Mix

    Our Pollinator Cover Crop Seed Mix features a varied mix of easy-to-grow legumes, including Clover, Alfalfa, Vetch, and Sainfoin. Small white, pink, purple, and gold flowers attract ...

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    Pollinator Cover Crop Seed Mix Balansa Clover, Berseem Clover, Yellow Sweet Clover, Sainfoin, Hairy Vetch & Alfalfa Trifolium michelianum Savi, Trifolium alexandrinum, Melilotus officinalis, Onobrychis vicifolia, Vicia villosa & Medicago sativa
    As low as $9.95
    Per 1 Pound
    Our Pollinator Cover Crop Seed Mix features a varied mix of easy-to-grow legumes, including Clover, Alfalfa, Vetch, and Sainfoin. Small white, pink, purple, and gold flowers attract and nourish pollinators. Hardworking legumes suppress weeds, fix nutrients into the soil, improve soil condition, and prevent erosion. This is an excellent choice for groundcover and covercrops, as well as lawn replacement, or adding to a wildflower meadow. All of the seed we carry at American Meadows is non-GMO, neonicotinoid-free and guaranteed to grow.
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  2. White Clover Seeds, Trifolium repens

    This legume is a vigorous, easy-to-grow clover that will produce large, white blooms. White Clover is perfect for using as a cover crop. Perennial. (Trifolium repens)...

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    White Clover Seeds White Clover Trifolium repens
    As low as $9.95
    Per 1 Pound
    This legume is a vigorous, easy-to-grow clover that will produce large, white blooms. White Clover is perfect for using as a cover crop. Perennial. (Trifolium repens)
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  3. Austrian Winter Pea Seeds, Pisum arvense

    This cover crop is low-growing and can be planted to help enrich soil, as well as prevent common garden weeds from coming up. It also delights with white, purple and red blooms. Ann...

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    Austrian Winter Pea Seeds Austrian Winter Pea Pisum arvense
    As low as $12.95
    Per 5 Pounds
    This cover crop is low-growing and can be planted to help enrich soil, as well as prevent common garden weeds from coming up. It also delights with white, purple and red blooms. Annual. (Pisum arvense)
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  4. Berseem Clover Close Up

    Berseem clover suppresses weeds, prevents erosion, and fixes nitrogen in the soil. Often called the “king of forage” Berseem germinates rapidly, grows quickly, and produces abund...

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    Berseem Clover Seeds Berseem Clover Trifolium alexandrinum
    As low as $4.95
    Per 1/4 Pound
    Berseem clover suppresses weeds, prevents erosion, and fixes nitrogen in the soil. Often called the “king of forage” Berseem germinates rapidly, grows quickly, and produces abundant biomass which breaks down to replenish organic matter. Attracts pollinators and other beneficial insects. A green manure crop that does not re-seed in the garden. (Trifolium alexandrinum)
    Learn More
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