Acacia irrorata grows as a tall shrub or small tree, to 12 m tall, mainly in dry or wet sclerophyll forest and on the margins of rainforest along the NSW coast, tablelands and western slopes. Also extends into QLD and Victoria.
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.
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 – from Greek akis, meaning a thorn or “thorny”.
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 vulnerable in Victoria. Not considered at risk in the wild in NSW.