Knob Thorn
Acacia nigrescens
Family:
Fabaceae, Pea Family
Form:
Tree; deciduous
Range:
Eastern and southeastern Africa
Habitat:
Low altitude woodland and wooded grassland
Living Desert Location:
African Aviary, East African Garden
Knob thorn is easily the most recognizable acacia, with or without foliage, due to the conspicuous knobs on the trunk and branches. The leaves are also a distinguishing feature in that the rounded leaflets are the largest of any African acacia. Spikes of sweetly- scented, cream-colored flowers occur in the spring, high in the canopy. These trees have an upright stature with a rounded crown generally reaching 30 to 40 feet in height. Some knob thorns can attain a height of over 70 feet and an age of over 300 years old.
The leaves and pods form part of the primary and/or secondary diet of elephant, giraffe, kudu, impala, grey duiker and steen-bok. It has been reported that browsed leaves of Acacia nigrescens release the hormone ethylene into the air. This is detected by nearby trees which respond by increasing the amount of bitter tasting tannins in the leaves to discourage the browsers. In times of famine, the leaves are served as spinach for human consumption.
The wood is very hard, heavy and durable. It’s a good wood for furniture, but difficult to cut. It is a good-quality fire wood, producing long-lasting coals that give off intense heat. The bark is used by some tribes for tanning leather. The inner bark can be used to make twine.
Deterrent for tree climbers.
