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Acacia decurrens is a tall shrub to tree, reaching 12 metres tall with a canopy to 5 metres or so wide.
It grows in dry sclerophyll forest or woodlands, with much of its existence in the central coast subdivision of NSW, extending to the central tablelands, southern tablelands and western slopes. It is considered to have naturalised outside of its main range, in SA, WA, Qld, Vic and Tasmania as well as other parts of NSW – commonly found on highway and freeway road verges.
It usually grows on heavier soils, often near creeklines. It can be a dominant midstorey plant in some woodland and forest vegetation, often with a mixture of age classes with dead trees and regenerating saplings.
The bark is green with green branches which have winged ridges.
Australian Wattles at least, can be broadly placed into 1 of 3 recognisable groups:
It is thought that Groups 1 and 2 are more highly evolved than Group 3.
This species is of Group 3: The leaves are compound-bipinnate (jacaranda-type), mid-green, to about 12 cm long with pinnules (leaflets) to about 1.5 cm long and much more widely spaced compared to other bipinnate wattles (somewhat resembling a hair-comb). The leaves typically have jugary glands but no interjugary glands.
Acacia spp. produce small 5-merous flowers, with 5 very small petals partly-fused into a short tube which sits above a fused calyx. The stamens are the main feature which are produced in high numbers per flower (staminate flowers), surrounding a single style. In this species, flowers are produced in globular heads, up to 7 mm diameter, with up to 35 very small staminate flowers per head. The heads are clustered into showy racemes and/or panicles, produced in the leaf axils and at the terminals, with many heads per raceme or panicle. Flowers are a rich bright yellow, with flowering usually starting in July-August. Trees are very showy when in flower.
Pods are straight to curved, to 11 cm long and about 1 cm wide. They are produced in large numbers and can cover the ground when shed.
An attractive flowering wattle but may be too big for some gardens. Also tends to be short-lived, prone to borer attack. They can tend to fall over at short notice. However, it can be used to create a privacy or screen at a high level. Will also create some light shade.
Flowers are heavily-visited by European Honeybees and probably native bees as well.
May be used in situations where establishing other medium trees is difficult. Grows very quickly.
Very hardy. Will tolerate sun and shade. Tolerates frost and hot weather. Not too fussy about soil although not often found naturally on very sandy soils.
Propagation is easy from scarified seed by covering with boiling water for 24 hours and discarding any seeds still floating on the surface.
Regenerates readily from bushfire through the soil seedbank.
Has been planted extensively in bushland regneration projects. Can naturalise outside of its natural area.
Acacia – from Greek Akakia – which refers to an Ancient Greek preparation made from one of the many species; the name of which derives from akis, meaning “thorn” – referring to the thorns of species in Africa.
decurrens – from the Latin meaning “decurrent” – where an organ extends down past the point of insertion. In this case, the leaf petioles extend down the stem as a ridge, a useful identification feature for this plant.
This species is not considered to be at risk of extinction in the wild.
NSW Flora Online – Acacia decurrens profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Acacia~decurrens
Australian National Herbarium – Acacia decurrens profile page http://www.anbg.gov.au/acacia/species/A-decurrens.html
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.