This is a clover, and one of the commonest yellow-flowered clover growing all over Scotland. As with all the clover species, named Trifolium in Latin, it has trefoil leaves, or leaves with 3 leaflets. It is an annual, self-seeding every year throughout grasslands and meadows. People find it easy to misidentify this as Black Medick. The difference is in the smooth, or glabrous, leaves and sepals of Lesser Trefoil, though stems can still be slightly hairy. Black Medick has unmistakably hairy leaves and sepals.
Leaflets are rounded but slightly notched at the tip. If exposed to a long summer of sunshine the leaves and stems can get ‘sunburned’, i.e. turn reddish in colour.
The flowers are tiny, about 4mm across, and clustered together in anything between 5 and 20 flowers to a flower head. These clusters grow at the ends of stems that sprout from the angles of the upper leaves. This is not to be confused with the Hop Trefoil, which is similar in structure, but the flowers are larger – about 8-15mm across, and more globular, having at least 20 flowers to a cluster. The Lesser Trefoil flower-head is quite loose by comparison.
Fruiting consists of a one-seeded pod which stays inside the calyx.
In Ireland this flower is known as the Yellow Shamrock.