Medicago lupulina (Black Medic, sometimes spelled Medick or Meddick; also known as Black Hay, Black Nonsuch, Blackweed, etc.) is a summer annual or perennial plant usually considered a weed. It has a tap root. Like other legumes, it has three leaflets; its center leaflet is on a separate petiole. As with other legumes, nitrogen-fixing bacteria, known as rhizobia, are found in nodules on the roots.