Vigna vexillata  var. vexillata is a creeping or climbing herb, with perennial stems and a spindle-shaped root. The stipules and stipels are egg-shaped to linear and sparsely hairy. The leaflets are arranged in threes (tri-pinnate); the leaflet stalk (rhachis) is up to 17 mm long with hairs similar to those on stems; the petiole is up to 82 mm long; the leaflets are either narrowly or broadly egg-shaped, diamond-shaped or linear, with a wedge-shaped or rounded base and a pointed or slightly blunt tip, up to 120 mm long and 46 mm wide, and with short, stiff, or soft appressed hairs.

Fig. 2. A tri-pinnate leaf of Vigna vexillata var. vexillata showing typical egg-shaped leaflets with wedge-shaped (rounded) bases and the twining stems. Photographed by Jonathan Swart.

The inflorescence is axillary, up to 180 mm long and with 2–3 flowers; the flower stalks are up to 2 mm long; petals are whitish-cream, mauve, pink, purple or pale with yellow nectar guides; the calyx is sub-equally lobed with the lobes often longer than the tube and covered with short stiff or soft brownish hairs; the pea flowers consist of a large standard petal that is asymmetrically rounded and with a notched apex, two wing petals that are more or less egg-shaped and a beak-like keel with a hollow spur (pocket) on the left-hand petal and the keel tip is twisted to the right through 180°. Nine anther filaments are united and one free and curved to the right. The ovary is attached directly at its base (i.e. sessile), is densely covered with soft, short hairs and curved upwards and to the right. The pods are cylindrical, up to ca. 120 mm long and 5 mm wide, densely covered in short, soft, or fine hairs, or almost without hairs, approximately 25-seeded. The seeds are kidney-shaped or square, up to 6 mm long and 3 mm wide, dark red to maroon to darkish-brown and mottled black to maroon.

Fig. 3. Long peduncles of Vigna vexillata var. vexillata. Photographed by Jonathan Swart.