Acacia saligna

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Coojong

Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Fabales
Family: Fabaceae
Genus: Acacia
Species: A. saligna
Binomial name
Acacia saligna
(Labill.) H.L.Wendl.

Acacia saligna (Syn. Acacia cyanophylla [Lindley]), commonly known by various names including coojong, golden wreath wattle, orange wattle, blue-leafed wattle, Western Australian golden wattle, and, in Africa, Port Jackson willow, is a small tree in the family Fabaceae. Native to Australia, it is widely distributed throughout the south west corner of Western Australia, extending north as far as the Murchison River, and east to Israelite Bay.

Coojong grows as a small, dense, spreading tree with a short trunk and a weeping habit. It grows up to eight metres tall. Like many Acacia species, it has phyllodes rather than true leaves; these can be up to 25 centimetres long. At the base of each phyllode is a nectary gland, which secretes a sugary fluid. This attracts ants, which are believed to reduce the numbers of leaf-eating insects. The yellow flowers appear in early spring and late winter, in groups of up to ten spherical flower heads.

A natural colonizer, Coojong tends to grow wherever soil has been disturbed, such as alongside new roads. Its seeds are distributed by ants, which store them in their nests to eat the seed-stalks. Disturbance of the soil brings them to the surface and allows them to germinate. Seeds germinate readily, and hundreds of seedlings can sometimes be found beneath a single parent tree. It is also extremely vigorous when young, often growing over a metre per year.

Acacia saligna has been planted extensively in semi-arid areas of Africa and the Middle East as windbreaks and for stabilisation of sand dunes. It also provides fodder and firewood.

[edit] Invasive potential

Acacia saligna has proven weedy when grown outside its natural range. It was planted in the northern suburbs of Sydney in the 1950s by well-meaning native plant enthusiasts and has naturalised in the area.

[edit] Environmental impact in South Africa

In South Africa, it proliferated at an uncontrollable rate, having been introduced to stabilise the sands of the Cape Flats outside Cape Town. It is regarded as the major harmful invasive alien plant in the Western Cape. The introduction of the acacia gall rust fungus, (Uromycladium tepperianum), has proven to be highly effective at reining it in. The acacia seed weevil,(Melanterius species) was introduced in 2001 and has now (in 2007) reached the stage where there are sufficient numbers available to begin its distribution. It is hoped that it will reduce the seed production to a level where there is not enough seed available for stands to regenerate at a high density after fires. It is also smoked by khoi tribes.

See also: Invasive plants of Australian origin

[edit] References

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