Previously known as Acacia nigrescens, the Knob thorn is an indigenous tree that grows to a height of between 5 and 18 m. The species has a wide distribution, occurring in the drier parts of South Africa as far north as Tanzania and is a familiar sight in the Kruger National Park.
The common names in English and Afrikaans refers to the very characteristic thorns of the tree. The thorns are hooked in shape and are ‘knobbed’, appearing on the trunks and branches. Deciduous, the tree has a cylindrical shape with a rounded crown. The foliage is a vibrant green colour and new growth sometimes has a bright red colour. Flowers appear before or with the new leaves during spring, providing a beautiful display. The yellowish white, scented flowers make way for fruit pods that turn black as they ripen. These pods are thinly textured and hang down in clusters.
The distinctive Knob thorn is drought and fire resistant, but sensitive to frost, especially when young. It has a moderate growth rate (approximately 600 mm per year) and is a good wildlife tree, attracting browsers and hole-nesting bird species.
An attractive shade tree, Senegalia nigrescens, will thrive in a large garden, planted away from building structures as the root system can be aggressive.