Burr medic
Medicago polymorpha

Decumbent or ascending annual, glabrous or pubescent; branches to 40 cm long.

Leaves 3-foliolate; leaflets obovate to obcordate; terminal leaflets 8–27 mm long, 7–20 mm wide, entire or toothed towards apex, sometimes with darker flecks or a basal darker patch; stipules deeply incised, glabrous or hairy on lower surface.

Inflorescences 1–3-flowered; peduncle shorter than to twice as long as subtending petiole. Calyx teeth longer than tube. Corolla yellow; standard 3–5 mm long; keel shorter than wings.

Pod cylindrical to truncate-conical or discoid, 2–10 mm long, 2.5–8.5 mm diam., coils 1.5–7; spines to 18 in a row, to 4 mm long, sometimes spineless or tuberculate; seeds 3–11.