Acacia dealbata
Acacia dealbata, commonly known as silver wattle, blue wattle or mimosa, is a species of flowering plant in the legume family, Fabaceae and is endemic to south-eastern mainland Australia. It is a bushy shrub or spreading tree with smooth bark, bluish grey or silvery and glaucous bipinnate leaves, spherical heads of yellow to bright yellow flowers, and straight to slightly curved pods. The Wiradjuri people of New South Wales use the name giigandul for the species.
Description
Acacia dealbata is an erect, bushy shrub or spreading tree that typically grows to a height up to and has smooth grey, brown or dark brown bark, deeply corrugated when old. The leaves are bipinnate, on a petiole up to long, with 6 to 30 pairs of pinnae, each with 10 to 68 pairs of narrowly oblong to linear pinnules long and wide. The leaves are bluish grey or silvery and glaucous. The flowers are borne in spherical heads in racemes or in panicle-like groups on a hairy peduncle long, each head with 13 to 42 yellow to bright yellow flowers. Flowering occurs from July to November, and the pods are straight to slightly curved, more or less flat and often slightly constricted between some or all of the seeds, slightly leathery, blue or purplish, with a white, powdery bloom.Taxonomy
Acacia dealbata was first formally described in 1822 by Johann Heinrich Friedrich Link in his Enumeratio Plantarum Horti Botanici Regii Berolinensis Altera.Along with other bipinnate wattles, A. dealbata is classified in the section Botrycephalae within the subgenus Phyllodineae in the genus Acacia. An analysis of genomic and chloroplast DNA along with morphological characters found that the section is polyphyletic, though the close relationships of many species were unable to be resolved. Acacia dealbata appears to be most closely related to A. mearnsii, A. nanodealbata and A. baileyana.
Some authorities consider A. dealbata to be a variant of Acacia decurrens.
The specific epithet means 'white-washed' or 'covered in a white powder'.
Subspecies
In 2001, Phillip G. Kodela and Mary Tindale described two subspecies of A. dealbata in the journal Telopea, and the names are accepted by the Australian Plant Census:- Acacia dealbata Link subsp. dealbata is a shrub or spreading tree up to with leaves mostly long, the heads with 22 to 42 pale yellow to yellow, sometimes bright yellow flowers.
- Acacia dealbata subsp. subalpina Tindale & Kodela is a dense shrub or tree up to, rarely to, with leaves mostly long, the heads with 13 to 34 bright yellow flowers.
Distribution and habitat
The species has been widely introduced in Mediterranean, warm temperate, and highland tropical landscapes.
As an invasive species
In the Western Cape of South Africa, the species is a Category 1 weed, requiring eradication; elsewhere in South Africa it is a Category 2 weed, requiring control outside of plantation areas. In New Zealand, the Department of Conservation classes it as an environmental weed. In Portugal and Spain, the species is listed as an official invasive species. In California, the species is invasive and appears to displace many native species, also threatening the habitat of the endangered Mount Hermon June beetle.Use in horticulture
Acacia dealbata is widely cultivated as an ornamental plant in warm temperate regions of the world, and is naturalised in some areas, including Sochi, southwestern Western Australia, southeastern South Australia, Norfolk Island, the Mediterranean region from Portugal to Greece and Morocco to Israel, Yalta, California, Madagascar, southern Africa, the highlands of southern India, south-western China and Chile. It is hardy down to, but does not survive prolonged frost. It prefers a sheltered position in full sun, with acid or neutral soil. It has gained the Royal Horticultural Society's Award of Garden Merit.Uses
The flowers and tip shoots are harvested for use as cut flowers, when it is known by the florist trade as "mimosa". In Italy, Albania, Russia and Georgia the flowers are also frequently given to women on International Women's Day. The essence of the flowers, called 'mimosa', or in older texts, 'cassie', is used in perfumes. The leaves are sometimes used in Indian chutney.In Australia, the Ngunnawal people of the ACT and Wiradjuri people of NSW used the bark to make coarse rope and string, the resinous sap for glue or to mix with ash to make poultices, the timber for tools, and the seeds to make flour. The timber is useful for furniture and indoor work, but has limited uses, mainly in craft furniture and turning. It has a honey colour, often with distinctive figures like birdseye and tiger stripes. It has a medium density, and is similar to its close relative blackwood, but of lighter tone without the dark heartwood.