Where you'll find this tree easily:

Black-thorn Acacia is the most prevalent smaller, woody species in the northern Cape, and eastward into the northern Bushveld. Where one is found there are often literally hundreds more.

 

Common names

• The Black-thorn Acacia is a low-branching tree with a dense V-shaped to wide-spreading canopy.
• The branchlets and twigs are dark, rigid and angular, and are intricately entangled.
• The devilishly hooked thorns are black on older branches, and green on younger ones.
• The bluish-green leaves are Twice Compound and small, despite the leaflets themselves being large for an Acacia.
• Creamy-white, sweet-scented flower-balls cover the tree in spring before the leaves appear.
• The straight, flat, papery pods are green when young and pale brown when ripe.
• The pods split open on the tree early in the season.

Seasonal Changes

Although deciduous, this tree can be identified throughout the year by its angular, intricately branched canopy and hooked thorns.

 

This is usually a multi-stemmed small tree with a canopy that sometimes touches the ground (3 – 7 m high).
 

Thorns

Short, curved thorns, like cats’ claws, are found just below each leaf-bud, and spiral around the branchlets and twigs. They are yellow-green when young and dark red to grey-black when mature. This tree has more thorns per length of stem than most Acacias (Thorn: up to 5 mm).

Leaves

The leaves have 2 – 3 pairs of feathers, and are unusual for an Acacia, each leaflet having only 1 – 2 pairs of large, opposite leaflets.  Each pair looks like a butterfly (Leaflet: 4 – 15 x 3 – 10 mm).

Bark

The bark is rough and dark brown to black on the main stem and older branches, with lengthwise fissures showing yellowish under-bark. On the young branches the bark is grey to yellowish-brown.

Flowers

The conspicuous flowers look like balls but are actually very short flower-spikes. They are closely packed along the rigid, dark brown branchlets (10 mm diam.) (Aug – Nov).

Pods

 The pods are tapered at the base with a rounded or bluntly pointed tip (Jan – Apr) (90 x 25 mm).
 

Gardening

This is an attractive addition to a water-wise, indigenous garden, but is very spiny so must be tucked away in a corner or can be used as a barrier. It grows moderately fast from seed, which must be soaked overnight in hot water before planting. The tree can tolerate a little frost and is drought resistant. It is suitable as a bonsai tree.

Human uses

IThe wood has been used for axe and pick handles. Since the heartwood is termite- and borer-resistant, the larger stems make excellent fencing posts. The sap of the Black-thorn Acacia was mixed with a powdered grub for use on Khoisan poison arrows. The gum is edible and is sometimes mixed with clay to make floors. Extracts of roots were used for the relief of stomach pains and to treat gonorrhoea. Extracts of the roots and leaves were used to treat colds, eye inflammation, diarrhoea and bleeding.
 

Links with animals

For more information on this tree and a wealth of others in the region, get a copy of the Sappi Tree Spotting Guide to the Cape - from Cape to Kalahari. Illustrations by Joan van Gogh/Penny Noall