Botanical Name: Acacia mollissima
Species: A. mearnsii
Taxonomic name: Acacia mearnsii De Wild.
Synonyms: A. decurrens var. mollis, Acacia mollissima
Habitat :Acacia mearnsii is native to Southeastern Australia and Tasmania, but has been introduced to North America, South America, Asia, Europe, Pacific and Indian Ocean islands, Africa, Europe, and New Zealand.
It has been introduced to numerous parts of the world, and in those areas is often used as a commercial source of tannin or a source of firewood for local communities. In areas where it has been introduced, it is often considered a weed, and is seen as threatening native habitats by competing with indigenous vegetation, replacing grass communities, reducing native biodiversity and increasing water loss from riparian zones. Found in tropical rainforests.
In its native range A. mearnsii is a tree of tall woodland and forests in subtropical and warm temperate regions. In Africa the species grows in disturbed areas, range/grasslands, riparian zones, urban areas, water courses, and mesic habitats at an altitude of between 600-1700m. In Africa it grows in a range of climates including warm temperate dry climates and moist tropical climates. A. mearnsii is reported to tolerate an annual precipitation of between 6.6 – 22.8 dm (mean of 6 cases = 12.6), an annual mean temperature of 14.7 – 27.8°C (mean of 6 cases = 2.6°C), and a pH of 5.0 – 7.2 (mean of 5 cases = 0.5). A. mearnsii does not grow well on very dry and poor soils.
Acacia mearnsii is a fast-growing leguminous tree.The trees are unarmed, evergreen and grow six to 20 meters high. The branchlets are shallowly ridged; all parts finely hairy; growth tips golden-hairy. Leaves dark olive-green, finely hairy, bipinnate; leaflets short (1.5 – 4 mm) and crowded; raised glands occur at and between the junctions of pinnae pairs. Flowers pale yellow or cream, globular flower heads in large, fragrant sprays. Fruits dark brown pods, finely hairy, usually markedly constricted.
The species is named after American naturalist Edgar Alexander Mearns, who collected the type from a cultivated specimen in East Africa.
Acacia mollissima plays an important role in the ecosystem in its native Australia. As a pioneer plant it quickly binds the erosion-prone soil following the bushfires that are common in the Australian wilderness. Like other leguminous plants, it fixes the atmospheric nitrogen in the soil. Other woodland species can rapidly utilise these increased nitrogen levels provided by the nodules of bacteria present in their expansive root systems. Hence they play a critical part in the natural regeneration of Australian bushland after fires.This plant is now known as one of the worst invasive species in the world.
Cultivation & Propagation:
A. mearnsii produces copious numbers of small seeds that are not dispersed actively. The species may resprout from basal shoots following a fire. It also generates numerous suckers that result in thickets consisting of clones. Seeds may remain viable for up to 50 years.
The invasiveness of this species is partly due to its ability to produce large numbers of long-lived seeds (which may be triggered to germinate en masse following bush fires), and the development of a large crown which shades other vegetation. Its leaves and branches may have allelopathic properties. A. mearnsii competes with and replaces indigenous vegetation. It may replace grass communities to the detriment of the grazing industry and grazing wildlife. By causing an increase in the height and biomass of vegetation A. mearnsii infestations increase rainfall interception and transpiration, which causes a decrease in streamflow. Soil under A. mearnsii becomes desiccated more quickly (than it does under grass). A. mearnsii stands also destabilise stream banks and support a lower diversity of species.
Commercial plantations and invasive stands of A . mearnsii in South Africa reduce surface runoff and decrease water ability, causing an estimated annual economic loss of $US 2.8 million. According to KwaZulu-Natal Wildlife (the governmental agency responsible for managing protected areas in KwaZulu-Natal Province, South Africa) the advance of alien plants (particularly Chromolaena odorata, Lantana camara, Acacia dealbata, and Acacia mearnsii) is the most significant past and future threat to conservation in these areas.
Edible Uses : Edible portion: Gum, Seeds. The gum is eaten and dissolved in water and used to make drinks.
Acacia mearnsii has some known medical applications, such as its use as a styptic or astringent. The planting of wattles has also been used as a soil stabiliser to decrease erosion (preferably far from river courses to minimise the water loss caused by the tree’s high rate of transpiration). The agroforestry industry promotes the use of Acacia mearnsii (among other similar species) as a potential “soil improver”. (Duke, 1983; Franco, 1971; Paiva, 1999; Tutin et al., 1992; de Wit, Crookes and van Wilgen, 2001; Young, 2002).
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The species is grown commercially in many areas of the world for a variety of uses, in addition to use as an ornamental. Commercial stands have been established in Africa, South America and Europe. The tannin compounds extracted from the bark of A. mearnsii are commonly used in the production of soft leather. A range of other products, such as resins, thinners and adhesives, can also be made from bark extracts. The timber is used for building materials, the charcoal is used for fuel and the pulp and wood chips are used to produce paper. In rural communities in South Africa the trees are important as a source of building material and fuel. Growers of the tree in that country banded together to form the South African Wattle Growers Union. A. mearnsii has some known medical applications, such as its use as a styptic or astringent. The planting of wattles has also been used as a soil stabiliser to decrease erosion (preferably far from river courses to minimise the water loss caused by the tree’s high rate of transpiration). The agroforestry industry promotes the use of the species (among other similar species) as a potential “soil improver”.The charcoal is extensively used in Brazil and Kenya, and in Indonesia the tree is extensively used as a domestic fuel and for curing tobacco.
Acacia mearnsii has been shown to contain less than 0.02% alkaloids.
The information presented herein is intended for educational purposes only. Individual results may vary, and before using any supplements, it is always advisable to consult with your own health care provider.