Medicago polymorpha aka Bur Medic

Medicago polymorpha is called bur medick or toothed burclover. It belongs to Fabaceae, the bean family. This shallow-rooted plant grows as an annual or short-lived perennial. Its native range includes Macaronesia, Europe, and Central Asia. It reaches western Nepal, northern Africa, and the Arabian Peninsula. It now also grows in Australia and the Americas. Roadsides, disturbed ground, and stream banks provide habitat.

Plants reach 1.5–2 feet [0.46–0.61 metres] in height. They spread 0.5–2.5 feet [0.15–0.76 metres] across. Many stems branch from the crown and form dense mats. Some lie flat, while others rise from the ground. The stems are pale green or tinged with red. White hairs cover young stems, but thin as plants age. Alternate leaves have three rounded leaflets with small teeth. Some show purple or white marks, or a small V.

Small yellow flowers grow in clusters at the stem tips. They bloom from March to June and draw pollinators. The fruit is a flattened, coiled legume with prickly burs. Ripe pods turn grey to black. Their hooks catch on clothes, fur, and sheep's wool. This helps carry seeds away from the parent plant. A large plant can form more than a thousand pods. Quail and deer feed on the dry burs.

Grow bur medick in full sun with soil that drains well. It also tolerates some shade, though PFAF advises against shade. PFAF favours light, dry soil with a neutral pH. NC State reports broader tolerance of soil and moisture conditions. Its listed soils include sand, loam, and clay. It also accepts acid, neutral, and alkaline conditions. NC State lists USDA hardiness zones 3–9. The plant grows fast and can spread beyond its planting site. It can become invasive, including as a lawn weed. NC State reports no major insect or disease problems.

Growers use bur medick for forage and orchard cover crops. Root bacteria fix nitrogen, giving it value as green manure. Leaving roots in place lets their nitrogen return to soil. People also grow it as a vegetable in China. Young leaves and shoots can be eaten raw or cooked. Only young leaves are listed for eating raw. Flowers are edible raw or cooked; seeds are eaten cooked. Roasted, ground seeds can make a mush with water. PFAF reports no known hazards, rather than proving universal safety. NC State records traditional medicinal use, but PFAF lists none.