Centro is a perennial herb that can reach a height of 45 cm (18 inches). Stems do not become woody until about 18 months after planting. Leaves are trifoliate, with elliptical leaflets approximately 4 × 3.5 cm (1.6 × 1.4 inches), dark-green and glabrous above but whitish and densely tomentose below. Flowers are generally pale violet with darker violet veins, born in axillary racemes. Fruit is a flat, long, dark brown pod 7.5–15 cm (3–6 inches) long, containing up to 20 seeds. Seeds are spherical, about 4–mm (0.16–inches) in diameter, dark brown when ripe.