The winter months provide the ideal opportunity to improve your garden’s soil. Planting winter cover crops (also know as green manure) can improve the garden’s soil’s upper layers.

Winter cover crops can increase organic matter content, prevent soil erosion, suppress weeds, help improve soil tilth, promote worm and microbial activity, benefit soil fertility, moisture, and texture, help control diseases and pests, and provide organic nitrogen production. Larger cover crops (such as farm crops) can curb wind erosion, too. While cover crops improve soil, crops also provide color to your yard, and protects and sustains to some beneficial, outdoor critters.

Types of cover crops

The following are the main cover crop categories: grasses (oats, wheat, etc.), legumes (cowpea, mung beans, etc.), brassicas (mustards, kale, etc.), and other broad leaves (flax, spinach, etc.)

Some of the more common cover crops are:

Cereal rye: Sow in late summer or early fall. Rye will grow in late fall, and begin growing again in spring.

Annual rye: Winterkills in USDA Plant Hardiness Zones 5 and colder.

Field peas and oats: Peas fix nitrogen, and oats provide organic matter. Peas and oats are cold tolerant. Plant in late summer or early fall. Will winterkill in colder climates.

Buckwheat: this smother crop protects against weeds. It grows quick and can shade out weeds. Squeeze between vegetable plantings. The buckwheat’s flower makes great filler in flower arrangements and when in the garden it attracts beneficial insects.

Clover: There are many sizes and shapes of clover -- “White Dutch clover works well as a living mulch, since it tolerates both shade and traffic. Yellow blossom sweet clover is an excellent nutrient scavenger and helps build good soil structure. Crimson clover attracts beneficials and looks great, too. Whatever the color, clover fixes nitrogen and helps to build rich soils.” – Organic Gardening

How to plant cover crops

“Make a furrow for larger or more vigorous seeds, such as cowpeas or sorghum-sudangrass, sow thickly, and then cover with soil. For smaller seeds, such as clovers, crucifers and small grains, scatter, rake in, and tamp the bed with the back of a garden rake to ensure good soil contact. To speed germination, apply a light mulch and water occasionally. Seeds of vigorous covers, such as annual ryegrass, oats and hairy vetch, will germinate if left on the surface, especially if broadcast just before a soaking rain.

You can plant a food crop as soon as the cover crop is killed unless there could be a temporary problem of allelopathy or nitrogen tie-up (keep reading for more information). In such cases, wait about three weeks or so before planting.” – Mother Earth News

For more information on how to pick, plant and use cover crops, consult Mother Earth News’ article, “Grow Cover Crops for the Best Garden Soil,” or the article, “Cover Crops: Options, Tips and Advantages for the home Garden.”

Resources:

http://www.uvm.edu/vtvegandberry/factsheets/covercrops.html

http://www.hort.cornell.edu/bjorkman/lab/covercrops/

http://www.agry.purdue.edu/ext/forages/publications/ay247.htm

Image: NRCS Soil Health