Black medic (Medicago lupulina) is a dark green annual with spreading, prostrate growth. Leaves are alternate with three leaflets on square stems. Leaflets are obovate to elliptic, toothed near the tip, and have a small spur on the tip. Bright yellow flowers are produced in tight, compressed clusters at leaf axils. Reproduction occurs via seed in tightly coiled black seed pods. This 2-page fact sheet was written by Barry J. Brecke, Ramon Leon, J. Bryan Unruh, and Darcy E. P. Telenko, and published by the UF Department of Environmental Horticulture, December 2014.
http://edis.ifas.ufl.edu/ep494