Acacia caffra (PROTA)

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bark (The Virtual Field Herbarium)
crown (The Virtual Field Herbarium)

Acacia caffra (Thunb.) Willd.


Protologue: Sp. pl. 4(2): 1078 (1806).
Family: Mimosaceae (Leguminosae - Mimosoideae)
Chromosome number: 2n = 26

Vernacular names

  • Common hook thorn (En).

Origin and geographic distribution

Acacia caffra is found mostly in northern and eastern South Africa and Swaziland, but occurs also in southern Botswana and southern Mozambique. It is found in small numbers near Harare in Zimbabwe, probably the result of an introduction long ago. It is planted in India.

Uses

The wood is used for fence poles and occasionally for furniture. The Xhosa people of South Africa used it for making traditional smoking pipes, and it also serves as firewood. The bark is used for tanning; it produces pale brown leather. Baskets are made from the twigs. A leaf decoction with milk is used by the Zulu people of South Africa as an enema to treat abdominal complaints in children; the leaves are sometimes chewed for the same purpose. A leaf decoction is also drunk to treat colds and fever. A bark infusion is administered as a blood purifier. Leaves and pods are eaten by livestock, but may cause poisoning.

Properties

The heartwood is dark brown and distinctly demarcated from the creamy sapwood. The texture is moderately fine to moderately coarse. The wood is heavy and hard. The density is 980–1060 kg/m³ at 12% moisture content. The wood seasons without serious defects.

A number of proteracacinidins (proanthocyanidins) have been isolated from the heartwood, and several cyanogenic glycosides from the leaves.

Description

  • Shrub or small tree up to 14 m tall; bole often twisted, up to 60 cm in diameter; bark rough, sometimes fissured, reddish brown to blackish brown; crown spreading; branchlets glabrous to densely hairy, with pairs of hooked prickles up to 9 mm long just below the nodes.
  • Leaves alternate, bipinnately compound, with 6–38 pairs of pinnae; stipules linear, 2.5–4 mm long, caducous; petiole 0.5–4 cm long, with gland near top, rachis 2–23 cm long, sometimes with prickles up to 3 mm long and with glands between top pairs of pinnae; leaflets in 16–64 pairs per pinna, linear to linear-oblong, 2–12 mm × 0.5–2.5 mm, oblique at base, with rounded to acute apex, glabrous to pubescent.
  • Inflorescence an axillary spike 2–10 cm long, solitary or in fascicles; peduncle up to 4 cm long.
  • Flowers bisexual, regular, 5-merous, small, creamy white, sessile; calyx campanulate, tube 0.5–1.5 mm long, lobes shorter; corolla campanulate, tube up to 2 mm long, lobes triangular, up to 1 mm long; stamens numerous, free, up to 6 mm long; ovary superior, 0.5–2 mm long, sessile or stalked, style slender, up to 6 mm long.
  • Fruit an oblong to linear pod 4.5–19.5 cm × 0.5–2.5 cm, usually straight, glabrous to hairy, reddish brown scaly, longitudinally dehiscent, up to 10-seeded.
  • Seeds flattened ovoid to oblong, 6–12 mm × 4–8 mm, olive green to pale brown.

Other botanical information

Acacia is a large pantropical genus, comprising more than 1300 species; most of them are distributed in Australia (more than 900), more than 200 in America, and about 130 in Africa. Acacia caffra belongs to subgenus Aculeiferum , which comprises all African Acacia species with non-spinescent stipules and hooked prickles. Acacia caffra is variable, especially in its indumentum, number of pinnae per leaf and leaflet size. It is sometimes confused with Acacia ataxacantha DC. and Acacia hereroensis Engl., the first of which has scattered prickles and the second smaller leaves and shorter petioles.

The seeds are probably dispersed by large herbivores such as elephants and antelopes and by baboons, all of which eat the pods.

Ecology

Acacia caffra occurs in open woodland, wooded grassland and on dry rocky hills, often along watercourses, up to 1500 m altitude.

Management

Acacia caffra coppices well.

Genetic resources

Although Acacia caffra is only found in the most southern parts of Botswana and Mozambique, it is widespread in South Africa and occurs there in a variety of habitats. Therefore, it is unlikely to be under threat of genetic erosion.

Prospects

Acacia caffra will remain only locally important as timber tree, but it has potential as a fast-growing and attractive ornamental which is drought- and frost-resistant.

Major references

  • Brenan, J.P.M., 1970. Leguminosae (Mimosoideae). In: Brenan, J.P.M. (Editor). Flora Zambesiaca. Volume 3, part 1. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 153 pp.
  • Coates Palgrave, K., 1983. Trees of southern Africa. 2nd Edition. Struik Publishers, Cape Town, South Africa. 959 pp.
  • Ross, J.H., 1967. Acacia caffra (Thunb.) Willd. in southern Africa. Webbia 22(1): 203–223.
  • Ross, J.H., 1975. Fabaceae, subfamily Mimosoideae. In: Ross, J.H. (Editor). Flora of southern Africa. Volume 16, part 1. Botanical Research Institute, Department of Agricultural Technical Services, Pretoria, South Africa. 159 pp.
  • Timberlake, J., Fagg, C. & Barnes, R., 1999. Field guide to the Acacias of Zimbabwe. CBC Publishing, Harare, Zimbabwe. 160 pp.

Other references

  • Bennie, L., Coetzee, J., Malan, E. & Ferreira, D., 2002. Structure and stereochemistry of dimeric proteracacinidins possessing the rare C-4(C) leads to C-5(D) interflavanyl linkage. Phytochemistry 59(6): 673–678.
  • Conn, E.E., Seigler, D.S., Maslin, B.R. & Dunn, J., 1989. Cyanogenesis in Acacia subgenus Aculeiferum. Phytochemistry 28(3): 817–820.
  • Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.

Author(s)

  • R.H.M.J. Lemmens, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Lemmens, R.H.M.J., 2006. Acacia caffra (Thunb.) Willd. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 27 November 2017.