Thursday, 1 September 2011

The Acacia Family

Acacia is a genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae, first described in Africa by the Swedish botanist Carl Linnaeus in 1773. [1] He also gave the species name of A.nilotica, for the range along, the Nile River.
The name (akakia) was given, by Greek botanist-physician Pedanius Dioscorides (ca. 40-90) to the medicinal tree, A.nilotica, in his book, Materia Medica. This name derives from the Greek word for its thorns (akis, thorn). [1] There is some debate on the Australians pinching our African name, but Professor Eugene Moll says; “We can still and quite correctly as far as I am aware, use the old names, as long as we quote the correct authors.” [2] Thomas Baines said in ‘Explorations in South-West Africa’ that he classified Thorn-Trees by putting them into different classes: “Class one, for tearing clothes; class two, for tearing flesh; class three, for tearing flesh and clothes both together.” [3]
Acacia robusta Burch. [4]
Tree No. 183 and 183.1
English name: Splendid Acacia/Broad-pod Robust thorn/Narrow-pod Robust thorn
Afrikaans name: Enkeldoring
isiZulu Name: umngamanzi; umnqawe [5]
The literal translation of the isiZulu name is ‘Stand by water’ [6]. The other Zulu name “umnqawe” is ‘smoking pipe’. This may mean, ‘that the wood for these pipes came from this tree’. If anyone knows the correct information, please inform us. This is a common tree, near rivers, and at the coast.  It is also fast-growing. One of the thorn-trees better suited to Durban’s climate, therefore better to plant in your garden, or in the Parks or in the streets. There are quite a few along the north bank of the uMngeni River.
The distinctive bark is rough and fissured and grey to dark brown. The spines are paired, straight to curved, short on old stems, usually 7mm to 20mm in length. {4 & 5} The flowers are white to cream scented balls, from June to September. They attract a lot of insects. Birds and monkeys also favour this tree. The bark is used for tanning and twine is made from the inner bark. [5] There is a Tree, currently, on the north bank of the uMngeni River, that is used for Muthi purposes. Only small pieces are taken off at a time, and in a way, that is not environmentally friendly, in other words, all the way around. So, the Tree is on the way to being ring-barked. We are not too sure, what is the medicinal value of this particular species? Does anyone have a clue? Possibly incense? Some other species of Acacias’ are used for ‘digestion’; ‘sic’.
Fodder and poison
Acacias are legumes, therefore soil improvers. It is said they greatly improve the protein in the grass, growing near. Under certain circumstances, Acacia robusta is only slightly poisonous. This is in the form of prussic acid. [3] If fresh plant material produces a certain amount of hydrogen cyanide, then it is potentially toxic. If the acacia “leaves” lack the cyanogenic glycoiside-slitting enzyme, that produces the cyanide, then they may be less toxic than otherwise. [1] The most poisonous of the Acacias are usually harmless, when they are browsed slowly by well-fed animals. They become dangerous, through overstocking and overgrazing. Prussic acid side-effects are also more poisonous if eaten faster. Wild animals or stock animals in the bush, are seldom poisoned, because the hardness of the pods, makes them eat slowly and in small amounts. The thorns act as a line of defence, as they prevent animals from browsing foliage and young pods too quickly. Some farmers gave their stock, sulphur/molasses as a protective measure against prussic-acid poisoning. The danger of this poisoning is increased by excess moisture. Dry leaves and mature pods contain less prussic acid. [3]
[3] Palmer, E. & Pitman, N. 1961. Trees of South Africa. A.A. Balkema, Amsterdam and Cape Town.
[4] Coates-Palgrave, K. 1981. Trees of Southern Africa. 2nd Impression. Struik Publishers, Cape Town.
[5] Boon, R. 2010. Pooley’s Trees of Eastern South Africa. 2nd Edition. Flora and Fauna Publications Trust. Durban
[6] Mzwandile Chili 

Rosemary Harrison

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