Acacia dealbata, commonly known as silver wattle, blue wattle or mimosa,
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
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 Acacia mearnsii, A. nanodealbata and Acacia baileyana.
Some authorities consider A. dealbata to be a variant of Acacia decurrens.
The specific epithet ( dealbata) 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
-
Acacia dealbata subsp. subalpina Tindale & Kodela
Distribution and habitat
Acacia dealbata is
native plant to New South Wales, Victoria,
Tasmania and the Australian Capital Territory, where it grows in forest or woodland in a variety of soils, often on slopes and creek banks.
Subspecies
subalpina has a narrower distribution from south of the Brindabella Range and Braidwood in New South Wales to the
Bonang River and
Gelantipy areas in north-eastern Victoria.
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, the species makes part of the official list of invasive species (along with other acacias).
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
temperateness regions of the world,
and is naturalised in some areas, including Sochi (Black Sea coast of Russia), southwestern Western Australia, southeastern South Australia, Norfolk Island, the Mediterranean region from Portugal to Greece and Morocco to Israel, Yalta (Crimea, Ukraine), California, Madagascar,
southern Africa (South Africa, Zimbabwe), the highlands of southern India,
south-western China and Chile.
[Michail Belov: [1], Chileflora. Consulted 2010, September 22.][Flora Europaea: Acacia dealbata][Jepson Flora: Acacia dealbata][ ] It is hardy down to ,
[ but does not survive prolonged frost.]
Uses
The flowers and tip shoots are harvested for use as cut flowers, when it is known by the florist trade as "mimosa" (not to be confused with the genus of plants called Mimosa). In Italy,
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.[Ngunnawal Elders (2014) 'Ngunnawal Plant Use.' ACT Government: Canberra][ 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 (540–720 kg/m3), and is similar to its close relative blackwood, but of lighter tone without the dark heartwood.
]
In culture
Acacia dealbata is one of the most readily-available for use in Wattle Day celebrations or commercial bouquets. It is also one of Hibakujumoku Australian plant species symbolically commemorated in Japan, allegedly being the first plant to bloom in the aftermath of the Hiroshima atomic bomb in August 1945.
==Gallery==
See also
List of Acacia species
