Acacia
Acacia nigrescens
Locally this tree is called msenjele (Swahili) and mng'enjele (Mwera), and its English name is knob thorn on account of the conspicuous woody spines on its trunk.
It can grow to a medium-sized tree but such individuals are now rare; smaller trees are still a common component of miombo woodland and thicket. It almost always has a single trunk. The bark is dark grey and slashing it reveals red sapwood underneath. Young branches are grey and hairy with short, dark pairs of hooked thorns. The leaves are compound with 6 pairs of smooth rounded leaflets held symmetrically, each leaflet having a prominent central vein. Its fragrant creamy white flowers are held in clustered spikes and appear with the new leaves before the short rains. These are followed by long flat brown pods.
This species might get confused with Zanthoxylon holtzianum as both have corky knobs on the trunk. A. nigrescens though has smaller knobs that do not grow as large as those of Z. holtzianum and do not form ridges. Also the leaves are much smaller and unscented.
Owing to its termite resistance, this is the preferred material for local house construction. The trunk is split lengthwise into rough sections, which initially have are reddish coloured but turn dark brown on exposure to air. The pale sapwood often is left attached when the poles are used as uprights in house building. The heartwood has historically been used to support mine shafts and as railway sleepers.
Often young trees are used top supply bark rope; however if all the bark is taken i.e. the tree is ring-barked, it will die. The leaves are eaten by game and also by people in times of food shortage.
Acacia nilotica
Acacia is from the Greek for a sharp point and nilotica refers to the habitat where it was first described by scientists. In English it is called the Egyptian thorn, or scented thorn.
The species is very variable in stature but is usually a multi-stemmed shrub and wooded grassland areas. It has prominent long, paired straight thorns. Notes that anything that looks like an Acacia but doesn't have thorns is not an acacia, and is probably an Albizia. It flowers mainly in the short rains, producing the fuzz balls characteristic of this sub-family. This species has sickly-sweet scented bright yellow flowers. The pods are sometimes curved, fleshy and hairy when young but becoming black when mature and releasing a sweet smell when crushed. The pods do not split along their length; instead they break up on the ground.
The timber is dark brown and very hard. It can be used to make mine shafts, but more usually it is used for tool handles. Formerly the pods were widely used to tan leather. Leaf extracts are used to treat a variety of medical complaints.
 A. nilotica tree
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 A. nilotica flowers
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 A. nilotica thorns
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