Virginia Tech Weed Identification Guide

Black Medic: Medicago lupulina

Weed Description:  A low-trailing summer annual, with yellow flowers.  Found throughout the United States, primarily a weed of turfgrass.
Seedling:  Cotyledons oblong (4-9 mm long).  First true leaf is borne on a single stalk, followed by leaves that consist of 3 leaflets and arise from a common point (palmately compound).
Mature Plant: Stems prostrate, 4-angled, hairy, radiating out from the taproot.  Compound leaves are alternate, with wedge- to oval-shaped leaflets.  Leaflets have toothed margins, are widest at the apex, and have a projecting tip in the center of the leaf.  The central leaflet is borne on a short stalk, while the lateral leaflets arise from the central petiole.   Stipules are present at the base of the petioles.
Fruit:  A kidney-shaped, 1-seeded black pod, 2-3 mm long and hairy.

Roots:   Taproot.

Flowers:  Small and yellow, in clusters, approximately 1/2 to 3/4 inches long.

 

Identifying Characteristics:   This weed may easily be confused with other weedy trifoliate legumes such as hop clover, large hop clover, yellow woodsorrel, etc.  However, the longer stalk of the central leaflet compared to lateral leaflets, small projecting tip at the leaflet apex, and toothed margins are important characteristics that help to distinguish black medic from other trifoliate legumes.