Acacia mearnsii

Black wattle

Family: Fabaceae subfamily Mimosoideae

A tree to 10 m or more tall, with a wide canopy spread potentially, with smooth bark.

It naturally occurs from Peats Ridge in NSW, extending south, through the coast and tablelands divisions, to Victoria, Tasmania, and South Australia. It has naturalised in Western Australia.

Found generally in wet and dry sclerophyll forest and woodland and coastal scrubs.

Australian Wattles at least, can be broadly placed into 1 of 3 recognisable groups:

  • Group 1: Those that produce juvenile compound-bipinnate leaves and then change to producing adult-phyllodes which are modified-flattened petioles which form the foliage. This is combined with flowers produced in globular balls or heads (or ovoid heads). The heads can be singular in leaf/phyllode axils or arranged in groups.
  • Group 2: As for Group 1 but flowers are produced in longer rod-like spikes.
  • Group 3: Those that never produce phyllodes and retain the juvenile compound-bipinnate foliage into adulthood. These always produce flowers in globular balls (which are secondarily arranged into panicle or raceme-like groups in many cases).

This wattle belongs to Group 3.

Leaves are compound-bipinnate (jacaranda-type), to about 14 cm long; dark, dull olive-green in colour, with each leaflet/pinnule less than 4 mm long and covered in fine hairs.

Flowers are first produced in globular heads, to about 8 mm diameter, with up to 40 very small staminate flowers per head, pale yellow, and fragrant.
The heads are arranged in axillary and terminal panicles or racemes, mainly produced in October to December.

Seed-pods are broad-linear, to 10 cm long, and about 1 cm wide.

In the garden

Considered easy to grow in sandy to loamy soils. It is a longer-lived bipinnate wattle with a nice overall form.

It has become a bad weed in many places including South Africa and the Americas. It is another wattle in Australia that will colonise roadsides very easily and has moved beyond its natural range.

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.

Other information

It is a useful pioneer plant that quickly binds erosion-prone soil following the bushfires and as well fixes the atmospheric nitrogen in the soil.

The species may resprout from basal shoots following a fire. It also generates numerous suckers that result in thickets consisting of clones. Seeds may remain viable for up to 50 years.

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.

mearnsii – named after Colonel Edgar Alexander Mearns (1856-1916), a notable American ornithologist and field naturalist who collected the type from a cultivated specimen in East Africa.

This species is not considered to be at risk of extinction in the wild.

Flora of NSW Online (PlantNET) – Acacia mearnsii profile page           http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Acacia~mearnsii

Wikipedia – Acacia mearnsii profile page                                 https://en.wikipedia.org/wiki/Acacia_mearnsii

Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.

By Jeff Howes. Editing and additional text by Dan Clarke.