Morphological Characteristics》《Knife Bean》,the interpretation of the name of the pods are shaped like a knife, so it is named Knife Bean. Planted in March, the vine can grow to one or two feet long, with leaves like those of the cowpea, but slightly longer and larger than those of the cowpea, purple flowers like moths in May and June, and pods, which are close to a foot long, somewhat like soap pods.

Cultivated subspecies of the genus Knife Bean, family Leguminosae, a twining annual herb. It is also the seed of the legume knife bean. Mature pods are harvested in the fall and winter, dried, and stripped of seeds for spare use; or young pods are harvested in the fall for fresh use. The dried mature seeds of the knife bean, alias knife bean seed, big knife bean. Cosmetics use its dried seeds. Twining herb, up to several meters long, glabrous or slightly hairy. Leaves pinnately compound with 3 leaflets, leaflets ovate, 8-15 cm long, (4-)8-12 cm wide, apex acuminate or with acute cusp, base broadly cuneate, both surfaces thinly puberulent or subglabrous, lateral leaflets oblique; petiole often shorter than leaflets; petiolules ca. 7 mm, hairy. Racemes long pedicellate, with several flowers borne above middle of rachis; pedicels very short, borne on nodes of raised inflorescence axis; bracteoles ovate, ca. 1 mm, caducous; calyx 15-16 mm, slightly hairy, upper lip ca. 1/3 as long as calyx tube, with 2 broad, rounded, cleft teeth, lower lip 3-lobed, teeth small, ca. 2-3 mm, acute; corolla white or pink, 3-3.5 cm, flag petals broadly elliptic, apically concave, base with inconspicuous auricles and broad petiole, winged and keeled petals both curved, with downward-facing auricles; ovary linear, hairy. Pods strap-shaped, slightly curved, 20-35 cm long, 4-6 cm wide, angled at about 5 mm from suture; seeds ellipsoid or long elliptic, about 3.5 cm long, about 2 cm wide, about 1.5 cm thick, testa red or brown, hilum about 3/4 of seed circumference.Flowering July-September, fruiting October.