The flowers of Indigofera nigromontana grow in few-flowered racemes on short stalks. They are small and mauve or pinkish purple, having a pea-flower shape. Flowers become about 1 cm long. The back of the standard as well as the five-lobed calyx is densely hairy. The flower centre is sometimes white. Flowering happens from winter to early autumn.
Small, straight and narrow pods are borne in an extended summer fruiting season. The dehiscent pods burst open when ripe, dispersing the seeds upon release.
This species is recommended in the literature as a garden plant (Vlok and Schutte-Vlok, 2010; JSTOR; iSpot; www.plantzafrica.com).