AgroForestryTree Database
Acacia saligna
 Species identityEcology and distributionPropagation and managementFunctional usesPests and diseasesAdditional InfoBibliographyImages |
Species identity
TaxonomySynonym(s)
Common names
(Amharic) : akacha saligna
(English) : blue-leafed wattle, golden-wreath wattle, orange wattle, Port Jackson willow, weeping wattle, willow wattle
Botanic description
Acacia saligna is a dense and multi stemmed, thornless, spreading shrub or a single-stemmed, small tree up to 9 m in height; bark is smooth and grey to red-brown on branchlets becoming dark grey and fissured with age. Leaves alternate, simple, flattened phyllodes, varying from very narrow to lance-shaped, about 10 times as long as wide, mostly 8-25 cm long and 0.5-2 cm wide, straight or slightly curved to the side, long, pointed and tapering at both ends like ribbons, hairless, often drooping, dull blue-green to whitish, with a permanent midvein and many fine side veins; large dotlike gland 1-2 mm or more in diameter at base of upper edge of phyllode. Flower clusters (heads) like balls, mostly 2-10 (sometimes 1), on stalks along axis (racemes) to 8 cm long at base of leaf; round, bright yellow or deep golden heads, 7-10 mm in diameter, with many (25-55) crowded, tiny flowers, abundant and showy; flowers stalkless, 3-4 mm long, mostly hairless, composed of calyx 1.5 mm long with conical tube and 5 short, rounded lobes, often finely hairy on edge; corolla of 5 narrow, long-pointed petals, 2-3 mm long, united near base; many threadlike stamens, pistil with hairless ovary and slender style. Fruits very narrow, 8-12 cm long and 4-6 mm wide, straight and flattened. There are 6 to 10 beanlike seeds, each 5-6 mm long x 3-2.5 mm wide, dark brown to black, shiny. The generic name ‘acacia’ comes from the Greek word ‘akis’, meaning a point or a barb. The specific name means ‘willowlike’ and describes the phyllodes.
Ecology and distribution
History of cultivationA. saligna was introduced to South Africa around 1876-1885 and to Libya for dune stabilization in 1920. In Ethiopia, it has been introduced to most medium and higher altitudes of the country through re-afforest ration programmes.
Natural Habitat
A. saligna grows mainly on sandy, coastal plains, but it is also found in a wide variety of environments, from swampy sites and river banks to small, rocky hills (often granitic) and slopes of coastal ranges. It is also found by creeks and disturbed roadsides. The plant tolerates salt spray, soil salinity and alkalinity. The associated vegetation types include open, dry evergreen forest, temperate woodland and semi-arid woodland.
Geographic distribution
Native : Australia
Exotic : Cyprus, Eritrea, Ethiopia, Greece, Iran, Iraq, Israel, Jordan, Libyan Arab Jamahiriya, Mauritius, Mexico, Namibia, South Africa, Syrian Arab Republic, Tanzania, Tunisia, Uruguay
Biophysical limitsAltitude: 0-300 m, Mean annual temperature: 23-36 deg C, Mean annual rainfall: 350-600 mm. Soil type: Occurs on many soil types, especially poor acid or calcareous sands. It will grow under the most adverse and dry soil conditions and in moderately heavy clays and a range of podzols.
Reproductive Biology
A. saligna is an out-crossing species.
Propagation and management
Propagation methodsA. saligna produces a large number of viable seeds, and young plants can often be found in their hundreds under mature trees, promoting the rapid spread of the species and directly contributing to its weed status. The seeds germinate easily. They are normally treated with boiling water for 1 minute, but nicking the seed coat, soaking seed in sulphuric acid, and exposing seed to dry heat are also effective. Successful micro-propagation techniques using tissue culture have also been used.Tree Management
Production for browse and wood can begin 3 years after planting out, gradually building to 6 years. The impact of various management methods on long-term productivity is not well understood. In Mauritius, the management options tried include trimming followed by direct grazing and direct browsing with periodic pruning. A rotation of 7-10 years or coppicing may be used. In Mediterranean countries, firewood from A. saligna is harvested on a coppice rotation of 5-10 years. Human interference and grazing should be discouraged for rapid success. Lupines should be sown where necessary to enrich the ground cover.
Germplasm Management
Seed storage behaviour is orthodox. There are about 14 000-25 000 seeds/kg.
Functional uses
ProductsFodder: The phyllodes, young shoots, pods and seeds, whether fresh or dry, are rich in protein and are non-toxic and palatable to both sheep and goats. They are particularly valuable seasonally when other forage is scarce. The chemical composition of the leaves shows dry matter (50-55%), crude protein (12-16%), crude fibre (20-24%), crude fat (6-9%) and ash (10-12%). Re-growth of established bushes is so good that A. saligna can be completely grazed off without harming the plant. Fuel: Plantations for firewood have been established in some Mediterranean countries. The wood is reported as sappy, light and not popular for firewood. A. saligna can withstand some shade and can be grown as an understorey beneath pines or eucalypts for energy in villages. Fibre: In Tunisia the wood has been successfully processed into particleboard. Timber: A. saligna is used for vine stakes and small agricultural implements. Gum or resin: The damaged bark exudes copious amounts of a very acidic gum that shows exceptional promise for use in pickles and other acidic foodstuff. Tannin or dyestuff: In the past, the tree was planted for tannin production from the bark.Services
Erosion control: A. saligna is one of the best species for binding sand. It has been used in North Africa, the Middle East and South Africa for coastal sand dune fixation, and in Uruguay for gully erosion control. Shade or shelter: A. saligna is useful for windbreaks. Reclamation: In Australia it has been used in the rehabilitation of sand mining areas. Nitrogen fixing: The tree nodulates with certain strains of Rhizobium. As with many other acacias, it forms associations with Vesicular Arbuscular mycorrhizal (VAM) fungi. Ornamental: A. saligna is widely planted as an ornamental.
Pests and diseasesVarious gall-exploiting insects invade the tree, and in parts of Western Australia more than 90% of the trees bear conspicuous galls. The trees are susceptible to white-scale insects, which attack the leaves and stems. Rodents sometimes attack the roots. Termites may cause serious problems in tropical countries. Older plants are susceptible to gall rust, Uromycladium tepperianum.
Bibliography
Bein E. 1996. Useful trees and shrubs in Eritrea. Regional Soil Conservation Unit (RSCU), Nairobi, Kenya.Bekele-Tesemma A, Birnie A, Tengnas B. 1993. Useful trees and shrubs for Ethiopia. Regional Soil Conservation Unit (RSCU), Swedish International Development Authority (SIDA).
Doran CJ, Turnbull JW (eds.). 1997. Australian trees and shrubs: species for land rehabilitation and farm planting in the tropics. ACIAR monograph No. 24, 384 p.
Erkkila A, Harri S. 1992. Silva Carelica Forestry in Namibia 1850-1990. University of Joensuu.
Hong TD, Linington S, Ellis RH. 1996. Seed storage behaviour: a compendium. Handbooks for Genebanks: No. 4. IPGRI.
Le Houerou NH. 1989. An assessment of the economic feasibility of fodder shrubs plantations (with particular reference to Africa). The Biology and utilization of shrubs. Academic Press Inc.
Little EL, Wadsworth FH. 1964. Common trees of Puerto Rico and the Virgin Islands. Agricultural Handbook. No. 249. US Department of Agriculture. Washington DC.
MacDicken GK. 1994. Selection and management of nitrogen fixing trees. Winrock International, and Bangkok: FAO.
Mbuya LP et al. 1994. Useful trees and shrubs for Tanzania: Identification, Propagation and Management for Agricultural and Pastoral Communities. Regional Soil Conservation Unit (RSCU), Swedish International Development Authority (SIDA).
National Academy of Sciences. 1980. Firewood crops. National Academy Press. Washington D.C.
New TR. 1984. A biology of acacias. A new source book and bibliography for biologists and naturalist. Oxford University Press. Melbourne.
NFTA. 1992. Acacia saligna: for dryland fodder and soil stabilization. NFTA 91-03. Waimanalo.
Witkowski ETF. 1991. Growth and competition between seedlings of Prate repens (L.) L. and the alien invasive, Acacia senegal (Labill.) Wendl. in relation to nutrient availability. Functional Ecology. 5: 101-110.