The distinction between the terms isn't terribly important as long as you choose the best plant for the purpose you have in mind. In September, most gardeners can plant overwintering cover crops. If you live where winters are mild, such as USDA Hardiness Zones 8 and south, you can plant and till under a green manure crop before planting a winter cover crop. Wherever you live, sow seeds of your winter cover crop at least 30 days before the last frost date in your region. In this article, I'll discuss cover crops you can plant in the fall and either till under in the late fall or overwinter and till under in spring.
Most gardeners know about the benefits of adding organic matter to the soil.
Many, as I do, build the soil with annual applications of compost, manure, leaves, and grass clippings. However, in some areas, those forms of organic matter may be difficult to find or transport. Cover crops not only add large amounts of organic matter, but they provide other benefits as well. Let's look at some of them. A primary reason to grow a cover crop is to increase the amount of organic matter in the soil.