Black Wattle Forest and Kim Starr/Flickr

Black Wattle

Acacia mearnsii

Did You Know?

  • Tannins and gums in the bark were used as adhesives by First Nations people and also to tan leather
  • Listed in the IUCN's top 100 of the world's most invasive species
  • Invasive in parts of Asia, southern Europe, southern Africa, New Zealand, Cook Islands and USA
FactBox Image

The Black Wattle plays an important role in Australia's ecosystems. As a pioneer plant it quickly binds erosion-prone soil following bushfires. Like other leguminous plants, it fixes the atmospheric nitrogen in the soil. Other woodland species can rapidly use these increased nitrogen levels provided by the nodules of bacteria present in their expansive root systems. Hence they play a critical part in natural regeneration after bushfires.

Spreading tree which grows to 5 - 15 m tall. Bark is smooth and of greenish-brown colour on young branches. Blackish and rough on trunk. Distinct yellow flowers in September to December.

Leaves

Fern-like bipinnate leaves (leaflets that are further subdivided in an arrangement of leaves on either side of the stem). Olive green in colour. Raised glands are present at the junction of and between each pinnae (little leaf).

Flowers

Pale yellow or sometimes cream coloured ball-shaped inflorescences (clusters of flowers arranged on a stem). Flowering occurs from September through to December. Highly perfumed.

Fruits/Seeds

Seed pods are dark brown to black in colour with a straight to curved shape. They are flat and are 3 - 12 cm in length and 4.5 - 8 mm wide. Seed pods are leathery to touch and strongly constricted between seeds.

Species: WhatToObserve Image

What to Observe

  • First fully open single flower (each ‘flower ball’ is actually a cluster of 20 - 40 flowers)

  • Full flowering (when 50% of flowers have opened)

  • End of flowering (when 95% of the flowers have faded)

  • No flowering

  • Open Seed pods (record all days)

Species: WhenAndWhere Image

When and Where

When To Look

  • From late autumn, throughout spring and early summer
  • Flowers appear from September to December
  • Seed pods appear after flowers

Where To Look

  • In every state except Northern Territory
  • Not native to Western Australia or Queensland
  • Tall woodlands and forests in warm temperate regions
  • Also found in open forests, woodlands or tussock grasslands
Species: WhatElse Image

What Else?

Similar Species

In Victoria only there are two similar species.

Silver Wattle (Acacia dealbata) only has glands at the base of the pinnae and generally flowers earlier. Black Wattle has darker green, non-silvery foliage.

Early Black Wattle (Acacia decurrens) is an introduced species native to NSW and is considered an environmental weed in Victoria. Its branches are angled and its dark green foliage has well separated pinnules.