Finished compost mixed into the topsoil encourages earthworms as does the food provided by a grass or leaf mulch. Planting fall cover crops such as clover or winter rye, and tilling them into the soil in spring, also will increase earthworm numbers. Leaves spaded into the soil during fall soil preparation will be eaten by earthworms and enrich the soil. Earthworms feed during the cool of the night and a light sprinkling of corn meal on the surface of the soil can promote rapid reproduction. Earthworms also will assimilate kitchen waste such as coffee grounds, vegetables and fruits lightly tilled into the soil.
Many gardeners measure the health of their soil by the number of earthworms.
Studies have shown that active worm populations boost plant production. According to United States Department of Agriculture information, an acre of land can host up to 500,000 earthworms that move up to 5 tons of soil in a year. With a life expectancy of 10 to 15 years, earthworms are more productive in the garden than at the end of a fishhook. Photograph courtesy of Judy Sedbrook.