Black Medick, Medicago lupulina

Life Cycle

Annual

Propagation

Producing only by seed.

Stems

Stems wiry, as much as 80 cm long and lying prostrate on the ground, or much shorter and erect or spreading.

Leaves

Leaves alternate (1 per node), compound with 3 small oval leaflets shallowly toothed at the tips and the central leaflet with a definite stalk (Figure 5, a) and the leafstalk (b) with a pair of thick stipules (c) at its junction with the stem.

Flowers and Fruit

Flowers individually very small but grouped in dense head-like clusters, about 1 cm in diameter, on long stalks from leaf axils. Each flower is very small, yellow (Figure 3). The seedpods are black (hence the common name), slightly coiled, prominently ridged and hairy or smooth. Flowers from early spring to late autumn, dropping its seed during most of that time.

Roots and Underground Structures

The root is slender but very tough and difficult to pull out or hoe off.

Habitat

Black medick occurs throughout Ontario in most soil textures. A particularly common weed in lawns, it also grows in gardens, waste places, roadsides, pastures and sometimes in cultivated fields.

Distinguishing Features

It is distinguished by its compound leaves having 3 oval leaflets, all with shallow teeth towards their tips but only the central one with a definite stalk (Figure 5). The small, nearly spherical clusters of yellow flowers on stalks usually longer than the leaves (Figure 3). The small clusters of black coiled seedpods produced from those flower heads.


Figure #1.

Drawing of whole plant.


Figure #2.

Cotyledon and first true leaf.


Figure #3.

Seedling plant.


Figure #4.

Mature plant.


Figure #5.

Trifoliate leaf.


Figure #6.

Small yellow flower.


Figure #7.

Seedpod.