Pretty and fragrant, the Earth-nut Pea hardly seems to be a weed, but it is - and moreover one which spreads by numerous underground stems. It is found chiefly in warm regions - in field, hedgerows, on fallow land, by the roadside as well as on dry banks and in thickets where it sometimes climbs to quite a height in search of the light. Or, finding no vertical support, it creeps and winds over the ground and surrounding grasses.

The Latin description tuberosus refers to the underground tubers that grow from the roots of the Earth-nut Pea and serve as storage organs. As soon as it germinates the young plant produces small branching rootlets.

Later round to oblong tubers appear at the points where the roots branch, increasing in size as they grow. It takes about four years for these to be fully developed and ripe. Dark and firm on the outside and practically pure white inside, they contain many reserve starches and sugars.

It is the distinctive shape of the flower which has given Forking Larkspur its name in many languages: to the Germans it looked like a knight’s spur (Rittersporn), as it did to the French (epe de chevalier); the Czechs discerned in it the foot of a magpie (ostro2ka straOka); and the English compared it to the spur of a lark’s foot. In some places the same common names were used for the closely related plants of the genus Delphinium with which this plant was sometimes classed.

The flowers of the Earth-nut Pea are an unusual shape and have a strong pleasant fragrance. At one time they were used to make a perfume not unlike the scent of roses. The leaflets are oval and terminate in branching tendrils that serve as organs of attachment to the support. The pods are up to 3 cm long and constricted behind each seed. The flowers are borne singly from June to September.

There are marked differences between separate populations of Knotgrass. This is a plant which often forms thick spreading carpets and stands up well to heavy usage. It therefore serves as a useful substitute for turf on playing fields and airfields.