Perennial climbing herb (generally grown as an annual). Flowers many-flowered racemes that are longer than the leaves. Flowers with corolla to 3 cm or so long, scarlet, sometimes with white wings, the beak twisted around 1-1.5 times. Leaflets over 10 cm long, ovate. Fruit elongated, to 20-30 cm or so long; seeds mostly broad, to about 2.5 cm long.
P. vulgaris is very similar but generally has smaller elongated seeds to 1.5 cm long; P. lunatus L. is the important edible Butter Bean (Lima Bean) from tropical S America. It is an erect or twining plant grown as an annual with white or yellow flowers and 2-4 kidney-shaped beans per pod.
Source: (2002). Fabaceae. In: . Horticultural Flora of South-eastern Australia. Volume 3. Flowering plants. Dicotyledons. Part 2. The identification of garden and cultivated plants. University of New South Wales Press.