Carissa bispinosa, the Karoo num-num, is a small tree or shrub up to 3 m. The plant, previously C. haematocarpa bearing large numbers of stout, forked thorns has been sunken into C. bispinosa.

The leaves of this form are hard, olive-green, ovate or elliptic and leathery. The bark is green and wrinkled. The flowers are small and white with short corolla lobes overlapping to the left. It blooms in spring and summer and the flowers are heavily scented. The ripe fruits are black and much eaten by birds (Coates Palgrave, 2002; JSTOR).