This creeping perennial is commonly seen in sand dunes or coastal turf in the South East, Moray Firth area, Western Isles and Galloway, but it also grows in the lime-rich inland grasslands of Eastern Scotland. Occasionally it can be found enjoying a chalky hillside.
It has softly hairy leaves which are pinnate, with 6 to 13 pairs of narrow smooth-edged leaflets. These end in a single leaflet, and not the tendril common to other species of vetch. The complete leaf is anything from 3 to 7cm long.
The blue-purple flowers are about 1.5cm long and grow together in tightly clustered racemes at the end of the stem. The flowers follow the usual pattern of pea-flowers, having one large petal at the top, two side petals like wings and a pair of fused petals at the base of the flower forming a ‘keel’ shape.
Like other members of the pea family, Purple Milk Vetch is a great nectar source for honey bees. Unfortunately it has been classed as Endangered on the Red List, having suffered the effects of chemical fertilisers throughout the 20th Century.