The beautiful, slow-growing camel thorn grows well in poor soils and in harsh environmental conditions. It is an ideal shrub/tree for a small or large garden. This is a protected tree in South Africa

Description
The camel thorn ranges from a 2 m spiny shrub to a 16 m robust tree. The stem is shiny reddish brown when young. The bark of a mature tree is grey to blackish brown and is deeply furrowed; bearing pairs of almost straight, whitish or brown spines. Spines often have swollen bases and appear at the bases of the leaves. The fully developed spines may be up to 60 mm long. The leaves are twice divided. There are normally 2 to 5 pairs of pinnae per leaf and 8 to 18 pairs of leaflets (pinnules) per pinna. They are hairless and have a prominent underside vein on the undersurface.

The tree bears bright yellow ball-like flowers that are sweetly scented. They are borne in late winter and last through to summer.

The fruit is variable and ranges from small and almost cylindrical to typically large, flat, thick, semicircular or half-moon-shaped pods. They are up to 130 mm long and 50 mm wide and are covered by velvety grey hairs. They are semi-woody, but spongy inside; the pods do not open even when ripe but fall to the ground in winter. Seeds are thick, robust and lens-shaped.

Distribution
This species is widely distributed inland, from the Northern Cape through to Limpopo Province. It also extends to Namibia, Botswana, Zimbabwe and to central Africa.

Name Derivations
Acacia is a very large genus of shrubs and trees coming from occurring all over the tropical world. The largest number of species in this genus is found in Australia where they have in the region of 900 species. The name Acacia comes from the Greek word for thorns, since a large number of species are thorny.

Acacia belongs to the mimosa family. This is the third largest woody plant family comprising about 100 tree species in South Africa . The other common member of this family is Albizia which is easily distinguished from Acacia in that the plants have no thorns. Both Acacia and Albizia are important ecological components throughout bushveld areas of the country.

Recent taxonomic developments in the genus Acacia indicate that the name Acacia as it pertains to Africa will soon change to give recognition to the differences between the Australian acacias and the African acacias. The African acacias will more than likely be divided into two separate genera, Vachalia and Senegalia, whereas the Australian members will retain the name Acacia.

Ecology
The camel thorn is a competitive species that can displace preferred vegetation. It has been assessed as potentially very highly invasive in Australia : climate predictions indicate that it could occupy large inland areas of northern Australia if allowed to spread.

This is a relict of the parental stock of African Acacia species and is one of the major trees, and frequently the only sizeable tree of the deserts of southern Africa . It is a long-lived plant that grows on sand in areas with an annual rainfall of less than 40 mm to 900 mm, and tolerates hot summer temperatures and severe frosts. In very dry areas Acacia erioloba occurs along watercourses or where underground water is present. The taproot can descend to 60 m, providing access to deep ground water.

Uses
The pods are useful fodder for cattle and are favoured by wild animals in Africa , especially elephants who chew the pods and disperse the seed in their dung. The timber is strong and is highly prized for firewood.

Dry powdered pods can be used to treat ear infections. The gum can be used for the treatment of gonorrhoea and the pulverized, burned bark can be used to treat headaches. The root can be used to treat toothache. To treat tuberculosis, the root is boiled for a few minutes and the infusion is swirled around in the mouth and spat out.

It is believed that lightning will strike at the Acacia erioloba more readily than other trees. The seeds can be roasted and used as a substitute for coffee; the gum is also eaten by humans as well as animals. The root bark is used by the Bushmen to make quivers. Many wild animals love to eat the pods and will rest in the dense shade, in the heat of the African sun.

Growing Acacia erioloba

Acacia erioloba can be propagated easily by seeds. The seeds generally need some treatment to weaken the protective waterproof seed coat. They can be put into boiling water and then left to soak for a couple of days until the seed swells. Alternatively the glossy coating can be lightly sanded before soaking. Seeds may then be sown in a well-composted, sandy seedling mixture, and kept in a warm and moist positon. Seeds usually take four to six weeks to germinate. It is also possible to propagate it with semi-hardwood cuttings, but this is not a commonly used method. Trees start to flower when about 10 years old.

References and further reading

• Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of southern Africa, edn 3 . Struik, Cape Town.
• Schmidt, E., Lötter, M. & McCleland, W. 2002. Trees and shrubs of Mpumalanga and Kruger National Park . Jacana, Johannesburg.
• Smit, N. 1999. Guide to the acacias of South Africa . Briza Publications, Pretoria.
• Van Wyk, A.E. (Braam). and Van Wyk, P. 1997. Field guide to trees of southern Africa . Struik, Cape Town.
• Venter, F. & Venter, J-A. 1996. Making the most of indigenous trees . Briza Publications, Pretoria.