Winter Cover Crops

green clover covered in snow
Clover is a great choice for a winter cover crop because it can thrive even in snow. Rashid Valitov/

Just because winter is on the way in, your family vegetable garden doesn’t have to be on the way out.

There’s a beneficial crop that can be planted in the fall in most sections of the country, will grow through the coldest months of the year and will benefit your soil when planting time arrives next spring.

This winter-hardy crop is a cover crop.

Cover crops are an Earth-friendly cornerstone of sustainable, organic gardening because they enrich the soil with large amounts of nitrogen and organic matter, helping to eliminate the need for chemical fertilizers. They perform this function particularly well in backyard gardens because homeowners typically grow them as annuals and then “turn them under” – tilling or hoeing them into the soil where they decompose quickly.

If this process sounds like making “green manure,” that’s exactly the role that annual cover crops play.

One of the best times to take advantage of the benefits of a cover crop is in the winter when many gardeners mistakenly think nothing will grow. What they don’t realize is that if nothing is growing in their garden there’s a good chance that winter rains and melting snows will leach the nitrogen and other nutrients in the soil below the root zone of next spring and summer’s crops. Cover crops offer an organic solution to this problem.

A non-legume cover crop, such as winter rye, for example, will take up nitrogen from the soil and keep it in the plant’s tissues. Then, when the rye is turned under in the spring, the stored-up nitrogen will be released into the soil where it can be used by the next crop.

Legume cover crops also add nitrogen to the soil. Unlike non-legumes, though, legumes take nitrogen from the air instead of the soil. When legumes are turned under in the spring the nitrogen they have stored up during the winter will be released into the soil in a form beneficial to succeeding crops and soil microorganisms.

Both non-legumes and legumes help prevent erosion and add organic manner to the garden.

There are four main categories of cover crops: grasses, other non-legumes, legumes, and mixtures.

Examples of non-legume cover crops are:

  • Rye
  • Oats
  • Wheat
  • Forage turnips
  • Buckwheat

Examples of legume cover crops are:

  • Clovers
  • Hairy Vetch
  • Field peas
  • Alfalfa

Winter cover crops that can be planted now include winter rye, hairy vetch, oats, rape/canola, clover (various kinds), alfalfa and Austrian winter peas. Some warm-season cover crops include Sudangrass and sorghum-Sudangrass, Japanese millet, cowpeas and soybeans.

Additional benefits of cover crops are that they:

  • Attract earthworms
  • Increase beneficial microorganisms in the soil
  • Attract pollinating insects
  • Help aerate the soil
  • Improve soil water retention

The selection of a cover crop depends on when it will be planted and the goal for its use. To choose the ideal planting time and cover crop in different parts of the country, gardeners might get the best results if they ask an organic gardening center in their area for a recommendation. Keep in mind that a blend of several cover crops might work best.

Cover crops can be turned under at various times, depending on local weather conditions and individual planting preferences for the next crop. As a rule of thumb, it’s best to wait at least two weeks after turning a cover crop under before planting the next crop.

There’s also a new no-till cover crop technique in which the cover cropped is chopped down and allowed to dry on top of the ground for 30 days. After that, you simply plant through the biomass.