Cover Crops

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Improve Your Soil with Cover Crops

At the end of the growing season you may be ready to rest, but your garden is not. One final effort can make a big difference: cover cropping. Even small gardens will benefit from the use of cover crops, or “green manures”. Tilling, weeding, harvesting and foot traffic of most home gardens tends to destroy soil structure. Planting cover crops is an easy way to revitalize the soil, and help soil tilth and subsequent plant growth. Cover crops are planted in vacant space and worked into the soil after they grow instead of being eaten. They provide a number of advantages to the otherwise wasteful use of space during your garden’s off-season.

Cover crops help to retain the soil, lessen erosion, and decrease the impact of precipitation on the garden by slowing the runoff of water. They also reduce mineral leaching and compaction, and suppress perennial and winter annual weed growth. The top growth adds organic matter when it is tilled into the garden soil. The cover crop’s root system also provides organic matter and opens passageways that help improve air and water movement in the soil.

Success in the growth of cover crops requires proper selection of the kind of cover crop, correct timing of seeding, and good management techniques. There are many traditional cover crops to select from, including annual ryegrass, winter rye, winter wheat, oats, white clover, sweet clover, hairy vetch and buckwheat. Grasses are easier to grow than legumes such as clover because they germinate more quickly and do not require inoculation. Small seeded crops are more difficult to establish than large seeded types such as oats and buckwheat. In poorly drained areas, grasses may be easier to get started. Winter rye and ryegrass grow in a very dense habit and are much more effective at shading out weeds than oats or small seeded legumes. Availability of seed and cost are other important considerations.

If sections of the garden are free during late spring or early summer, clovers, fescue or buckwheat can be planted. If garden space is available in August, barley, annual ryegrass, oats, and clover can be successfully established. The last date when cover crops can be planted in New York will vary with the region, but most New York gardeners should plan to plant cover crops by the end of September. By the beginning of October, only rye and winter wheat can be productively started.

Cover crops such as annual ryegrass, oats, and buckwheat do not overwinter. These crops are the easiest to work with when spring arrives since their tops have died back during the winter. Perennial ryegrass and winter rye produce a massive amount of top growth in the spring and may be difficult to incorporate. However, perennial grasses are an advantage in wet areas, since the soil will dry more rapidly than a soil with winterkilled crops. If this is the case, before the leaves grow too tall in the spring they should be cut back once with a mower or scythe.

Given all of the above information, how does one choose? For New York conditions, annual ryegrass should be considered first for a garden cover crop. It is a vigorous grower with an extensive root system that occupies the same root zone as the garden plants. Winter rye is another good choice that is best for late planting.

To plant a cover crop, rake the garden area smooth and remove debris or large stones. Broadcast the seed according to the rates on the chart below. Lightly rake again, and water in the cover crop with your hose set at a fine mist.

The following chart provides an overview of the cover crops at a glance. Seed can be purchased at your local garden center or farm store.

 POPULAR AND USEFUL CHOICES OF COVER CROPS
Vigor of
germina- tion &
establish- ment
Seed cost to plant (1000 sq.ft) Time of planting Over-winter ability Growth amount Ease of
incorpor- ation
Soil structure improve- ment Applic. rate; oz/ 100sq ft Comments
Annual Ryegrass *** * Aug – Sept NO ** **  *** 2 Overall an easy crop to establish
Perennial Ryegrass ** ** Aug-mid Sept *** ** * ** 1 Faster establishment than other perennials. Extensive root system
Winter Rye *** ** Aug – Oct *** *** * ** 3 Can Grow at low pH and at cool temperatures
Oats ***  ** Aug – Sept NO * *** * 4 Requires good soil drainage, but tolerates low pH
Winter Wheat *** ** Aug – Oct *** *** * ** 3 Requires fertile soil; avoid wet or low pH soil
Sweet Clover * * Summer *** *** ** ** 1 Better with high pH than other clovers
White Clover * *(*) Summer *** * *** ** 1 Good for low pH soil, treat with inoculant
Tall Fescue * *** Spring *** * ** ** 1 Persistent, may become weedlike
Buckwheat *** ** Spring NO ** *** * 3 Do not allow to mature,or reseeding will occur
*** = Relatively High
** = Moderate
* = Relatively Low
 Note: Packages of Ryegrass Usually Contain a Mixture of Annual & Perennial Types


Ecogardening Factsheet #9, Spring 1993

Updated 11/2011