Medicago lupulina

Native to Asia, Europe, Northern Africa, and the Indian Subcontinent. Introduced and naturalized in North America.

Disturbed sites.

May to September

Yellow

8″ to 32″

This is a low annual or biennial forb that rises on multiple stems from a taproot.

The stems are sprawling, ascending, or erect, hairy, and 4-angled.

The leaves are alternate and compound, divided into 3 leaflets. They are on short leaf stalks. The leaflets are elliptical to egg-shaped with the attachment at the narrow end, ⅜″ to ¾″ long and wide. The terminal leaflet is on a stalk ⅛″ or more long. Leaflet margins are finely-toothed. The tip of each leaflet is notched and bears a small spine. The upper surface is sparsely hairy, the lower surface is hairy.

The inflorescence is many globular, head-like clusters at the end of long, unbranched, leafless, stalks rising from the leaf axils. The stalks are 1 to 4 times longer than the subtending leaves. The flower heads are ¼″ to almost ½″ across. Each head has 10 to 50 flowers.

The flowers are pea-like, with 5 petals organized into a banner, 2 wings, and a keel formed by two petals fused together at the tip. The keel is smooth, not grooved. The petals are yellow. The individual flowers are stalkless.

The fruit is a black, kidney-shaped seed pod containing a single seed.

Palmate hop clover (Trifolium aureum) has leaflets without a notch or spine at the tip. The terminal leaflet is attached without a stalk.