Medicago polymorpha L., burclover, is a shallow-rooted annual legume. The characteristic growth habit of burclover is one of numerous prostrate stems branching from the crown and spreading outward 6 to 30 inches. Where thick stands develop stems may become erect, obtaining heights of 18 to 24 inches in more favorable years. The leaves are subglabrous and clover-like in appearance, with leaflets normally wedge-shaped and toothed toward the top. The inflorescence is usually quite limited, presenting only a few small, yellow, pea-like flowers. The several-seeded fruit is a flattened, coiled pod, commonly up to 1/4 inch in width and fringed with a double row of conspicuous, hooked spines. Well developed plants may produce more than 1,000 pods. The seed is rather large for a legume of this type, usually developing to over 3/32 inch in length.
Although often considered an indigenous California plant, burclover was introduced from southern Europe. Burclover has become extensively naturalized in the United States from cultivation as a hay or cover crop. It is one of the more widely recognized Medicago species, especially west of the Sierra Nevada and Cascade Mountains, where it is most abundant.
Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).