Acacia polyacantha Willd.

Home

Leguminosae

Synonyms

  • Acacia campylacantha Hochst. ex A. Rich.
  • Acacia catechu (L.) Willd.
  • Mimosa suma Roxb.
  • Acacia caffra Willd. var campylacantha Aubrév.
  • Acacia campylacantha (Hochst. Ex A.Rich.) Roberty
  • Acacia catechu Oliv.
  • Acacia suma Benth.
Author: Le Houérou

 

Description

Tree reaching 15 to 21 m in height. The trunk with fissured, ash-grey bark, with brown scales and black knots on the place of insertion of former leaves and thorns. Slash red-brown with white streaks. Knobbly persistent prickles in pairs below each node, straw coloured to brown or black, with a black tip, 4 to 12 mm long. Leaf petiole glandular up to 25 cm long, with 10-40 pairs of pinnae bearing 15-60 pairs of leaflets each. Leaflets 4-6 mm long and 0.5-1 mm wide. Petiole broadening to 5 mm at the bottom with a large gland between the second and third pairs of pinnulae, occasionaly with small, solitary spines. Flowers cream or white in spikes 6-12 cm long set in pairs or triplets. Pods brown, dehiscent, 7-18 cm long, 1-2 cm wide, flat, dark brown, containing 5-10 seeds that can be seen through the translucent wall. The tree has a good germination capacity and quick juvenile growth.

Soil

Deep fresh soils medium textured to clayey, well drained, neutral to alkaline, occasionally on compacted hard soils and stony slopes.

Distribution

Widespread in tropical Africa from the Gambia to Eritrea, Ethiopia, in the north, to the Transvaal in the south. A subspecies, polyacantha, occurs in India. A. polyacantha is suspected to have been introduced from the Indian sub-continent.in the olden days, and now completely naturalized. This is not the only such case, see Tamarindus indica.

In the Sudanian and Guinean savannas, restricted to well watered places in the South Sahel ecozone, around ponds and in the bottom of fossil valleys with a shallow water-table, but sensitive to water-logging. Not a gregarious nor very common species. A. polyacantha is a tree of the sub-humid to humid African tropics with a wide distribution from South Senegal to Ethiopia and East Africa.

Crop management

In spite of its feeding quality, it is a most undesirable tree; has strong, pernicious, recurved spines, and spreads rapidly on fallow land in pasture, particularly on low-lying fertile alluvial soil along the drainage lines (in Zambia). It is expensive and difficult to eradicate. Large trees can be killed by ringbarking and the application of arboricides.

Products & uses

Hard durable wood ; sapwood white, heartwood red with blackish streaks ; service wood, poles, posts, various tools, handles, wheels etc. easy to polish, but difficult to saw. Good fuel wood and charcoal, gum edible, heartwood chips are used for tanning and dyeing, ashes are a substitute for salt. Human medicine : roots are an antidote to snakebite, bark decoction used for dysentery, to cure veneral diseases and gastro-intestinal disorders, a tonic beverage is made from the roots. Trees are pollarded for forage.

Links for the genus:

References

Aubréville 1950 ; Berhaut 1975 ; El Amin 1973 ; El Amin 1990 ; Geerling 1982/88 ; Kerharo & Adam 1974 ; Weber et al 1977 ; Von Maydell 1983/86 ; Vassal 1998 ; Dommergues et al. 1999.