Orange wattle is an extremely rugged tree, adaptable to barren slopes, derelict land, and exceptionally arid conditions in Australia and North Africa. It grows rapidly and is used for reclaiming eroded hillsides and wastelands and for stabilizing drift sands as well as for fuel. This is one of the best woody species for binding moving sand. It is useful for windbreaks, amenity plantings, beautification projects, and roadside stabilization in semiarid regions. The leaves, or phyllodes, are palatable to livestock when fresh or dried into hay, especially used as supplementary feed for sheep and goats. Crushed seeds have been fed to sheep without ill effects. Regrowth of established bushes is so good that Acacia saligna can be completely grazed off without harming the plants. The damaged bark exudes copious amounts of a very acidic gum that seems to show promise for use in pickles and other acidic foodstuffs (NAS, 1980).
No data observed.
Natal-grown bark contains up to 30.3% tannin compared to 19.1–23.0 at the Cape. The plant has given negative test for HCN.
Dense, bushy shrub, usually 2–5 m tall; may grow treelike to 8 m tall with a single main stem (diameter to 30 cm). In spring its usually drooping branches are clad in beautiful and abundant yellow flowers (NAS, 1980a).
Reported from the Australian Center of Diversity, orange wattle, or cvs thereof, is reported to tolerate alkalinity, drought, heavy soil, poor soil, salinity, salt spray, sand, shade, slope, waterlogging, and weeds. (2n = 26)
Acacia saligna is native to the southwestern corner of western Australia. It was introduced to South Africa in the 1840s in an attempt to stabilize the shifting sand dunes. It has also been planted in Uruguay, Mexico Israel, Iran, Iraq, Jordan, Syria, Greece, Cyprus, and North African countries (NAS, 1980a).
Acacia saligna can grow throughout the tropical and the warm temperate regions of the world (NAS, 1980a). In its native habitat, the summer temperature ranges from about 23°–36°C, winter temperatures from 4°–9°C. The plant does not withstand frost and grows best where the winter and summer means are between 13° and 30°C respectively. Grows from near sea level to about 300 m, with isolated occurrences at higher elevations. Particularly drought hardy, it grows where annual rainfall is as low as 250 mm, though it probably does better with 350–600 mm. It grows well where annual rainfall is as high as 1,000 mm. Grows mainly on sandy, coastal plains, but is found from swampy sites and riverbanks to small, rocky hills (often granitic) and coastal slopes. It occurs on poor acid or calcareous sands, under the most dry and adverse soil conditions, in moderately heavy clays and a range of podzols (NAS, 1980a).
Seeds germinate readily; young plants can often be found under mature trees in the hundreds. Seedlings are easily raised in a nursery and established in the field. This species develops root suckers and coppices freely. Seeds are normally treated with boiling water, but nicking the seed coat, soaking in sulfuric acid, and exposing the seeds to dry heat are also effective (NAS, 1980a).
In Mediterranean countries, the fuelwood from this species is harvested on a coppice rotation system of 5–10 years (NAS, 1980).
Acacia saligna grows quickly, often reaching up to 8 m tall with a spread as great as its height in just 4 or 5 years. In very dry situations, growth rate is slower. Annual yields vary from 1.5 to 10 m3 per ha, depending on site. Because of its hardiness and profuse reproductive abilities, Acacia saligna has become a serious menace in parts of South Africa by invading and displacing indigenous vegetation. It infests water courses (sometimes decreasing the water available for irrigation), and has proved difficult to eradicate (NAS, 1980a).
Plantations for fuel have been established in some Mediterranean countries. But, according to one report from South Africa, the wood is “sappy, light, and not a popular fuelwood.” The plant can withstand some shade and can be grown as an understory beneath pines or eucalypts in energy plantations or village fuel and fodder areas (NAS, 1980a). The annual litterfall of four Acacia species naturalized in the South African Cape, comprising 60% foliage and 30% reproductive structures, averages 7 MT/ha, double the value expected in evergreen scrub communities in winter rainfall regions.
Acacia saligna supports a diverse and abundant range of herbivores that cause damage to the plant. Among pests cited are Icerya purchasi (Hemiptera) and Euproctis fasciata (Lepidoptera) (NAS, 1980a) and Meloidgogyne sp. (Nematoda)
- N.A.S. 1980a. Firewood crops. Shrub and tree species for energy production. National Academy of Sciences, Washington, DC.