The flat pea or narrow-leaved everlasting-pea is native to parts of Africa, Europe, and Asia. Its natural habitat is forest edges, sparse broad-leaved hillside forests, dry hillside meadows, hedgerows, embankments and waste grounds. It uses its tendrils to scramble over plants, shrubs and the lower branches of trees.
The flat pea is a perennial plant which can grow 200 cm by climbing with its tendrils. The inflorescence has a long stem and three to ten pinkish-red flowers. The fruit is a slender pea pod about 5 cm long, initially flat and green, plump and brown at maturity, and containing 5 to 15 seeds.
The fruits and, to a lesser degree, the foliage, contain the toxic amino acid oxalyldiaminopropionic acid and if eaten in large quantities can cause ‘lathyrism’, a serious disease. Symptoms appear as a paralysis of the muscles below the knees, pains in the back, followed by weakness and stiffness of the legs and progressive locomotive incoordination.