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Leguminosae-mim Acacia tortilis ssp. (Forssk.) Hayne heteracantha (Burch.) Brenan

Leguminosae-mim Acacia tortilis
| | © Rosemary Wise

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Species information

Interest
The wood is heavy (890-990 kg/m3) and mostly consists of yellowish sapwood. The red-brown heartwood is usually confined to irregular small patches and is very heavy and hard. It seasons well except around the pith. A. tortilis makes a good firewood while the inner bark is used for cordage. Young branches are used for bush fencing. Subsp. heteracantha grows moderately slowly and is cold resistant. Its drought resistance is probably a result of a well-developed root system. The seeds geminate well after some form of scarification and the plant establishes readily, but not in the shade of its parents. The pods are a much relished source of browse for both wildlife (antelope, giraffe, monkeys and baboons) and livestock, particularly goats, and contain up to 17% protein. Seeds have a hard seed coat and are presumably adapted to withstand the mastication and digestive processes and are readily dispersed in droppings. Yield data are not yet available for Zimbabwe, but for maximum production of pods and grass tree numbers per hectare should be kept low. In some rural areas pods are gathered to feed livestock. Leafy shoots are also browsed by cattle antelope and giraffe, however the long thorns reduce browsing and more thorns can be produced under high browsing pressure. Leaves remain on the plant into the dry season, thus increasing its value as a forage source. Said to produce an edible gum eaten by bushmen, and possibly also the leaves and pods (without the seeds). Fibres beneath the coarse outer bark are chewed to alleviate thirst.

Other Notes
Species characteristics: Medium to large tree to 21 m tall, or sometimes a multistemmed shrub or bush, crown typically flattened and spreading, but sometimes rounded (ssp. raddiana) and more open. Has spirally twisted indehiscent pods, both hooked and long straight stipular spines, and whitish fragrant flowers in round inflorescences. The species is vary variable, seperated into six infraspecific taxa including four recognised subspecies on the basis of glands and hairs on the pods and young branchlets and crown shape. This species can dominate many savanna communities and provides an important source of browse for wild and domesticated animals. Found scattered on old sand dunes and rocky scarps, or in deciduous woodland on deep alluvial calcareous soils often indicating a higher water table or drainage lines. It can also occur on lateritic gravels, saline and sodic soils, and often colonises disturbed sites. Used in silvipastural systems, sand dune stabilisation and shelterbelts, as well as fuelwood, honey source, tannin, gums for medicine, cordage and constructional uses in nomadic societies. It is planted as an exotic in Rajasthan, India and Pakistan. In Africa, it is often the tree that extends furthest into the Sahara desert. Common names: Angola: Munponde (Lunyaneka); Mozambique: Sessana (Changane), Sessane (Changane); Namibia: Haak-en-steek (Africaans), Omungondo (Herero); Zimbabwe: Mukhu (Chikorekor). Distribution : Angola (Mocamedes, Namibe); Botswana (Northern Division, Central, South East, Ngamiland, Ghanzi, Kweneng, Kgalagadi); Mozambique (Sulo do save, Gaza, Maputo); South Africa (Transvaal, Natal, Cape, Orange Free State, Pietersburg); Swaziland ; Zimbabwe (Buhera, Gwanda, Beitbridge, Hwange, Hurungwe, Nyamandhlovu, Chiredzi, Chipinge, Matobo, Chimanimani, Mwenezi, Mutoko); Namibia (Kaokoland, Damaraland, Grootfontein, Namibrand, Rehoboth, Windhoek, Otjiwarongo, Maltahohe, Okahandja, Karibib, Outjo, Kavango). Specimen total: 453 Degree squares: 85 Collection years: 1818-1996 Phenology: Flowering period: Jan(53), Feb(10), Mar(5), Apr(5), May(1), Jun(3), Aug(1), Nov(19), Dec(47); Fruiting period: Jan(35), Feb(11), Mar(25), Apr(25), May(19), Jun(20), Jul(16), Aug(5), Sep(2), Oct(2), Nov(14), Dec(25) Altitude range: 30-1400m

Specimen information

Collector
PS

Specimen Number
s.n.