Earthworms and Nightcrawlers in the Home Lawn

Earthworms and nightcrawlers are considered beneficial because they aid in the decomposition of turfgrass thatch and grass clippings, which helps to recycle nutrients and organic matter into a lawn’s soil. The tunneling and burrowing caused by earthworm activity provides a natural cultivation effect that is much more effective than that experienced with mechanical core cultivation/aeration equipment. These tunnels help oxygen and water to enter the turf root zone more easily.

Unfortunately, earthworms are regarded by many homeowners to be pests because their burrows and castings can cause a lawn surface to become anywhere from slightly to extremely bumpy.

Several species of earthworms are found in the U.S. The nightcrawler, Lumbricus terrestris Linnaeus, and the red earthworm, Lumbricus rubellus Hoffmeister, are the most common larger species. Smaller species belong to the genera Allolobophora and Eisenia. Earthworms are generally found in the top 12″ to 18″ of the soil because this is where food is most abundant. The worm ingests soil and organic matter that is swallowed and ground in the gizzard. The ejected material (called castings) is used to line the burrow or is deposited at the entrance (on the lawn surface). Earthworm activity is greatest when soil is warm and moist, becoming active when soil thaws in the spring. The worms will move deep into the soil if it becomes dry during the summer.