It forms a dense clump of pointed leaves with purple flowers in spring, shading to a greenish-blue with age.

[2] This species,[3] and the cultivar 'Alboroseus',[4] have gained the Royal Horticultural Society's Award of Garden Merit.

The leaf blades are pinnate with two to four pairs of ovate tapering leaflets with blunt tips, entire margins and no tendrils.

The uppermost petal is known as the "standard", the lateral two as the "wings" and the lowest two are joined to form the "keel".

It can be distinguished from bitter vetch (L. linifolius) and black pea (L. niger) by the breadth of its ovate leaflets.