Problem: Black Medic (Lawns)
Medicago lupulina This annual weed is also called yellow trefoil or black clover, the latter because of its cloverlike leaves and black seeds. It is common in lawns throughout the United States in June, July, and August. Black medic reproduces by seeds and has a shallow taproot. It usually invades lawns with poor, sterile soil in which lawn grasses don''t grow or grow poorly. If not controlled, a single black medic plant enlarges into a thick mat that crowds out lawn grasses.
Improve the soil fertility by following a program of regular feedings during the growing season.