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Acacia irrorata grows as a tall shrub or small tree, to 12 m tall, spreading to several metres wide – sometimes with a narrow habit.
It grows mainly in dry or wet sclerophyll forest and on the margins of rainforest, mainly along the NSW coast, as far south as Bermagui. There are a few records in the tablelands and western slopes areas. It extends into Queensland, as far north as Gladstone and as far west as areas such as Warwick. It seems to only just occur in Victoria, to the east of Orbost, with much disjunction from Bermagui in NSW. It is critically endangered in Victoria.
Australian Wattles at least, can be broadly placed into 1 of 3 recognisable groups:
Phyllodes and bipinnate leaves are always alternate to clustered, never opposite.
This wattle belongs to Group 3.
Leaves are compound-bipinnate (Jacaranda-type), dark green, to about 15 cm long. Pinnae (groups of leaflets) are about 5 cm long (coming off main leaf axis) with individual pinnules (leaflets) about 5 mm long by less than 1 mm wide. Most of the leaf rachis (mid-part) lacks the presence of jugary glands, a primary identification feature. The leaves have a genreally nice feathery feel.
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. Flowers in all bipinnate wattles are produced in globular heads with the heads then arranged in raceme or panicle like groups. Heads in this species are about 7 mm diameter, containing up to 50 very small, staminate flowers, pale yellow to cream- coloured. The racemes can contain many heads and emerge from leaf axils and at the terminals.
Seed pods are straight to slightly curved, sometimes twisted, to 12 cm long and to about 1 cm wide.
Garden cultivation conditions not known. Other bipinnate wattles are known to grow very readily in the garden.
Acacias can suffer from a number of pests, including borers, scale, galls and leaf miners. Growing plants suitable to your local environment minimises these occurring.
Propagation is easy from scarified seed by covering with boiling water for 24 hours and discarding any seeds still floating on the surface.
Most wattles regenerate from seed after fire and some exhibit basal suckering.
Similar to Acacia mearnsii and A. parramattensis, it can be distinguished by only having 1 to 4 jugary glands on the leaves (between pairs of pinnae) at the top of the leaves and none further down the leaves (although it can sometimes have a gland at the basal pair of pinnae).
Two subspecies are currently recognised in NSW:
– subsp. irrorata (typical and widespread subspecies).
– subsp. velutinella (which grows on the North Coast subdivision of NSW).
They differ on the number of jugary glands and flowering times.
Acacia is a highly diverse genus, with over 1500 recognised species (placing it in the top-10 most-diverse plant genera) occurring in most continents except for Europe. Australia has about 970 spp., most of which are endemic. There are also about 10 exotic species. NSW has about 235 recognised species. Some species have become weeds in other states outside of their natural range (e.g., wattles from Western Australia into NSW and vice versa).
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.
irrorata – means ‘to bedew’, as if covered with dew. This may refer to the colour of the foliage or the hairs on the leaves that give it such an appearance.
Classified as threatened with extinction (critically endangered) in the wild in Victoria. Not considered at risk of extinction in the wild in NSW.
NSW Flora Online (PlantNET) – Acacia irrorata profile page http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Acacia~irrorata
World Wide Wattle – Acacia irrorata profile page http://worldwidewattle.com/speciesgallery/irrorata.php