Some farmers and gardeners plant a "cover crop" in the fall to protect and improve their soil in the period between fall and spring. Most cover crops planted in the fall in Missouri are winter annuals. Some of the common winter annual cover crops in Missouri are winter rye, winter wheat, crimson clover, hairy vetch, and various members of the mustard family. These cover crops are normally planted with a grain drill on farms, but home gardeners can broadcast them on tilled soil and then rake the area to cover most of the seed with at least a little soil. While the cover crops may not grow much in the fall, their roots still help hold the soil in place. In early April the cover crops will begin to grow rapidly. In the case of legume cover crops, if allowed to grow until sometime in May, the legumes will produce some nitrogen that helps the fertility of the following farm or garden crop.
At the farm we have used a variety of cover crops. Each has it advantages and disadvantages. On my own home garden I use crimson clover because it's easy to establish by broadcast seeding, produces it's own nitrogen (when inoculated at seeding), produces attractive flowers in May, and is easy to control before planting a following crop. However, crimson clover doesn't like wet, saturated conditions, and is not quite as reliable as winter rye or even winter wheat. Some of the mustard type cover crops have tap roots that help loosen the soil. Any cover crop can help improve the organic matter in the soil and suppress early season weeds. If you have an area of the garden that won't be planted until late May or June, you can plant a spring cover crop in late March or early April that will have a couple of months to grow; several different clovers or Austrian winter peas can be used, as can spring oats or spring wheat. Gardeners who grow primarily cool season vegetables that are done by July may plant a late summer cover crop such as buckwheat or foxtail millet that will grow until fall but be killed by frost.
Some good sources of cover crop seed are:
Peaceful Valley Farm Supply
Albert Lea Seed (for larger quantities of seed)
by Rob Myers