The genus Carissa consists of evergreen shrubs and trees, with handsome, glossy foliage and fragrant, starry-white, jasmine-like flowers. Ornamental and edible, scarlet to crimson oval fruits are produced after flowering. Carissas are attractive, ornamental shrubs and make excellent hedges.

Carissa haematocarpa commonly known as Karoo num-num grows into an evergreen shrub or small tree of up to 3 meters tall. It has large numbers of stout, forked thorns and is found mainly inland in the Western and Eastern Cape Karoo. It can also be found growing in the Richtersveld and adjacent southern Namibia areas. The leaves are hard, olive-green, ovate or elliptic and leathery. The bark is green and wrinkled. The flowers are small, white, with corolla tubes of 7 mm and broad, 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.