Acacia nilotica (acacia)

The wood of Acacia nilotica was used by ancient Egyptians to make statues and furniture.

Illustration of flowers and leaves of Acacia nilotica
Spiny branches with leaves and pompom inflorescences (Image: RBG Kew)

Species Information

  • Common name(s): acacia, Egyptian mimosa, Egyptian thorn, red thorn. Babool, babul (in India). Burkill gives at least 129 different names for this plant as a whole or for the fruit and seeds.
  • Conservation Status: IUCN status: ‘Least Concern’.
  • Known hazards: The leaves and fruits can be poisonous of eaten in large quantities.
  • Habitat: The species can withstand extremely dry environments and can also endure floods. It thrives under irrigation. Some African subspecies occur in wooded grassland, savannah and dry shrub forest. Other subspecies are restricted to riverine habitats and seasonally flooded areas. The subspecies nilotica is adapted to periodic flooding followed by extended droughts. It grows at elevations from sea level to 1500 m, although only to 500 m in the Himalaya mountains. It prefers alluvium soil but also grows well on heavy, clay soil with a pH range of 5 to 9.

Taxonomy

  • Kingdom: Plantae
  • Division: Magnoliophyta
  • Class: Magnoliopsida
  • Order: Fabales
  • Family: Leguminosae
  • Genus: Acacia

About this Species

This species has been used since early Egyptian dynasties. Disocorides (the Greek philosopher, physician and ‘father of botany’ c.40 to 90 A.D.) described in his ‘Materia Medica’ a preparation extracted from the leaves and fruit pods. He called this ‘akakia’, and it is from this word that the modern name is derived. The origin of the name Acacia means 'spiny' which is a typical feature of the species. Acacia nilotica is the type species for the genus, although after the Vienna 2005 International Botanical Congress, this issue is highly controversial. There is hence a current debate concerning whether to call this species Acacia nilotica or Vachellia nilotica, which name is correct under the current Code of Botanical Nomenclature.

Geography & Distribution

  • There are nine subspecies of Acacia nilotica, which occur in Africa (two in southern Africa), India and Pakistan.

Acacia nilotica is native to Africa. It is widely spread in subtropical and tropical Africa from Egypt to Mauritania southwards to South Africa, and in Asia eastwards to Pakistan and India. It has been introduced in China, the Northern Territory and Queensland in Australia (where it is considered to be a pest plant of national importance), in the Caribbean, Indian Ocean islands, Mauritius, United States, Central America, South America and the Galápagos Islands). It has naturalized in several countries where it has been introduced as a medicinal, forage and fuel wood plant.

Description

More Information
Acacia nilotica tree

Acacia nilotica tree (Image: Jonathan Timberlake)

A small to medium tree, 7 to 13 m tall, with a stem diameter of 20 to 30 cm. The crown is low, spreading and almost symmetrical, and can be flattened or a rounded umbrella-shaped (in free standing specimens). The bark is very dark brown to black with deep regular vertical grooves in older specimens. The thorns are almost straight, paired at the nodes of the stem and usually pointing slightly backwards.

The leaves are bipinnate, 4.5 to 7 cm long, with 2 to 14 pairs of pinnae. The pinnae are 1.5 to 7 mm long. The trees generally lose their leaves during the dry season, though riverine subspecies can be almost evergreen.

The flowers are bright yellow and borne on globe-shaped flower heads. The flowers are sweetly smelling and appear near the beginning of the rainy season. Flowering is prolific, and can occur a number of times in a season. Often only about 0.1% of flowers set pods.

The nutritious pods retain their seeds at maturity and are dispersed by animals. The pods are compressed, slightly curved, and vary from slightly constricted to almost rosary-like (like a string of beads). The pods are smooth or covered with fine hairs. A mature tree can produce 2,000 to 3,000 pods in a good fruiting season, each with eight to sixteen seeds, yielding 5,000 to 16,000 seeds per kg, depending on the subspecies.

Important synonyms: Mimosa arabica Lam.; Mimosa scorpioides L.; Mimosa nilotica L.; Acacia scorpioides W. Wight, Vachellia nilotica (L.) P.J.H. Hurter & Mabb.

Threats & Conservation

More Information

Acacia nilotica is a pioneer species, easily regenerated from seed, and it is not considered to be threatened. The species can become a weed when introduced out of its native range, particularly in more humid zones. Thorniness can be a problem when introduced to areas where people do not traditionally use thorn trees.

A wide range of pests and diseases affect this species. The stem borer Cerostema scabrator is a pest of economic importance on young plantations in India. Euproctis lunata and E. subnotata occasionally defoliate patches of forest in Sukkur and Hyderabad. Bruchid beetles attack the seeds, destroying up to 70 % of them. Buprestid beetles cause a dieback disease in Sudan. Fungal rots (Fomes papianus and F. badius) attack unhealthy trees, and powder post beetles (Sibixylon anale and Lyctus africanus) attack the sapwood of felled timber. Many wild mammals feed on seed pods and a large number of insect species attack the mature seed.

  • Medicinal (human and animal)
  • Cattle fodder
  • Charcoal
  • Construction
  • Emulsifying agent and emollient
  • Driving away evil spirits (shamanism)

Acacia nilotica has a wealth of medicinal uses. It is used for stomach upset and pain, the bark is chewed to protect against scurvy, an infusion is taken for dysentery and diarrhoea. In Nigeria it is one of the standard drugs for treating diarrhoea. It has also been used to eliminate stomach worms, as an antiseptic for open wounds and as an expectorant for treating coughs. The species has also been used in veterinary medicine, for example as a molluscicide to reduce liver-flukes in cattle. The pods are desirable as fodder for cattle, and the leaves, young shoots and young pods are thought to aid milk production.

Acacia nilotica inflorescences
Acacia nilotica inflorescences (Image: Jonathan Timberlake)

Acacia nilotica wood burns without too much smoke and provides good charcoal. The flowers provide both pollen and nectar for bees. The species is suitable for live fencing, mine timber, railway sleepers, boat building, wheels, water wells and so on as its wood is durable and resistant to borers and termites. The sap-wood and heart-wood was used in ancient Egypt for house beams, furniture, panelling and statues as it was regarded as impervious to insect and fungus attack. The bark contains tannins and has been used to preserve and soften leather. Photochemical analysis has shown the presence of two types of tannin (gallotannins and catechins) which explain its therapeutic action as well as its use in tanning hides.

Gum is present in the bark but tends to be dark in colour. This species may indeed have been the original source of the true gum arabic which is now obtained commercially from Senegalia senegal. The Acacia nilotica gum, samogh or samuk (arabic) is sold in boles and it is commercially of inferior quality. It has been used as an emulsifying agent and emollient. It is edible and is used to relieve throat and chest complains.

Babul (subspecies indica) is a popular farm tree of the central plains of India. More recently interest has centred on the fastigiate form (subspecies cupressiformis). This subspecies makes an ideal windbreak to surround fields as its narrow crown shades less than other windbreak species.

In shamanism Acacia nilotica has been used to drive away evil spirits.

Acacia nilotica seed pod
Acacia nilotica seed pod (Image: RBG Kew)

Extracts of the pod have been found to be active against two fresh-water snails (Bulinus truncatus and Biomphalaria pfeifferi), which are vectors of the parasitic disease schistosomiasis in Sudan. A pilot scheme to produce ‘tan’ (a vegetable molluscicide) has been set up. This is a water extract in which tannins amount to over 56% of the product, and are probably the active ingredient.

In Senegal Acacia nilotica is considered an important tree in the forest reserves along the banks of the Senegal River. In Sudan and the Upper Nile region it has been planted as part of the reforestation of the areas alongside river banks, which are subject to flooding.

In India this species is used extensively on degraded saline/alkaline soils, growing on soils up to pH 9, with a soluble salt content below 3%. It also grows well when irrigated with tannery effluent, and colonises waste heaps from coal mines. Over 50,000 hectares of the Indian Chambal ravines have been rehabilitated with A. nilotica by aerial seeding (it is one of the three most frequently used trees for this purpose). In India, too, A. nilotica is an important tree for lac insects  - lac being used as a dye and as shellac, a glazing agent.

Millennium Seed Bank: Seed storage

More Information

Kew's Millennium Seed Bank partnership aims to save plant life world wide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in our seed bank vault.

Number of seed collections stored in the Millennium Seed Bank: 15
Seed storage behaviour: Orthodox - the seeds of this plant survive being dried without significantly reducing their viability, and are therefore amenable to long-term frozen storage such as at the MSB
Germination testing: Successful
Composition values: Oil content 3-10.6%, Protein 18.2-23.4%

Description of seeds

Subcircular in outline, 6-9 x 5-8 mm, with areole (pleurogram) 5-7x 4-7 mm. The seed is free of tannins, but contains mucilage and sugars. They also contain a dark yellow fixed oil at a concentration of 5.46 %.

Seed from natural populations of some subspecies are available from India and some Sahelian countries. A broader range of germplasm and Rhizobium inoculum, is available from the Oxford Forestry Institute (Oxford OX1 3RB UK) for field trials.

Cultivation

More Information
Illustration of Mimosa nilotica

Illustration of Mimosa nilotica, a former name for A. nilotica, Dr Woodville (1791). (Image: RBG Kew)

Acacia nilotica is a slow-growing species but is moderately long-lived. It is easily established from seed, but it needs scarification (the hard seed coating must be subjected to mechanical abrasion or hot water treatment), especially if the seeds are not fresh. Seeds generally germinate fast (7-15 days). The seedlings need full exposure to sunlight and a free-draining soil.

The species will tolerate only light frost, but is extremely resistant to drought and heat. It is also tolerant of saline soil. Young trees coppice well, and the species can be propagated from truncheons, root suckers and cuttings. Some subspecies can be invasive (and can be extremely invasive in exotic habitats). The species can be direct seeded or established by seedlings. In the nursery long poly-tubes (20 x 7 cm) should be used so as not to restrict rapid tap root growth. Frequent root pruning is advised. Nursery grown seedlings are usually planted out after six months, but in some cases stay in the nursery for up to a year. Establishment varies depending on the site. Seedlings are shade intolerant.

In irrigated plantations in the Sind and Punjab, 10-15 seeds are spot sown at 2 x 3 m spacing on the tops of trenches. They are thinned to three to four seedlings after three to four months. Further thinning occurs at five year intervals. Rotations are 20-25 years. In the Thal desert, Pakistan (where there is 250 mm annual rainfall), promising growth resulted from irrigation of ten day intervals. Growth rates varied considerably depending on the sites, with maximum mean annual increment of 13 m3 /ha at 20 years old and 10.5 m3 /ha at 30 years recorded.

Useful Links


References & Credits

Burkill, H.M. (1995). The useful plants of West Tropical Africa : vol 3 families J – L. Royal Botanic Gardens, Kew. 857 pp.

Ellery, K. & Ellery, W. (1997). Plants of the Okavango Delta: a field guide. Tsaro Publishers Durban. vi, 225 pp.

Fagg, C.W. & A. Greaves.1990. Acacia nilotica 1869-1988. CABI/OFI Annotated bibliography No. F42. CAB International, Wallingford, Oxon, UK 77 pp.

Sheik, M.I. (1989). Acacia nilotica (L.) Willd. ex Del. Its production, Management and Utilization. Pakistan. Regional wood energy development programme in Asia, GCP/RAS/111/NET Field document no. 20, FAO, Bankok 10200, Thailand. 45 pp.

Spicer, N., Barnes, R. & Timberlake, J. (2007). Acacia handbook. DFID Forestry Research Programme, U.K.

Timberlake, J., Fagg, C. & Barnes, R. (1999). Field guide to the Acacias of Zimbabwe. CBC Publishing, Harare 160 pp.

Tybirk, K. 1989. Flowering, pollination and seed production of Acacia nilotica. Nordic Journal of Botany 9: 375-381.

Kew Science Editor: Lulu Rico

While every effort has been taken to ensure that the information contained in these pages is reliable and complete, the notes on hazards, edibility and suchlike included here are recorded information and do not constitute recommendations. No responsibility will be taken for readers’ own actions. Full website terms and conditions.



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