ClimateWatch

An initiative of Earthwatch Institute

  1. Acacia-mearnsii-large-plant-by-forest-andkim-starr-flickrcc Acacia-mearnsii-plant-by-Forest-andKim-Starr_FlickrCC

Black Wattle

Acacia mearnsii

Appearance

Description: Spreading tree which grows to 5-15m 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 3-12cm in length and 4.5-8mm wide. Seed pods are leathery to touch and strongly constricted between seeds. 

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)

ClimateWatch Science Advisor

Plants are expected to alter their shooting and flowering periods as a result of climate change impacting temperature and rainfall. They may also start appearing in new areas, as climate change enables them to live in environments that were previously unsuitable for them. 

Help scientists answer the question: "How are our animals, plants and ecosystems responding to climate change?"

 

When To Look

From late autumn, throughout spring and early summer

Flowers appear from September to December 

Seed pods appear after flowers

Note: ClimateWatch is looking for any changes in the timing of these events so remember to keep a lookout all year!

 

Where To Look

In every state except Northern Territory. Not native to WA or QLD.

Found in tall woodlands and forests in warm temperate regions but can be found in most environments under several different conditions, from open forests, woodlands or tussock grasslands.

Note: ClimateWatch is looking for any changes outside of their known ranges so remember to keep a lookout beyond these regions too!

 Black Wattle distribution map - GBIF

Black Wattle distribution map - GBIF

Sightings

References

Acacia mearnsii, Flora of Victoria. https://vicflora.rbg.vic.gov.au

Acacia mearnsii, Yarra Ranges. http://fe.yarraranges.vic.gov.au

ClimateWatch Science Advisory Panel

Links

  1. Search Species

  1. What Else?

    Acacia dealbata (Silver Wattle) - glands on the foliage are a key difference: A. dealbata only has glands at the base of the pinnae. A. dealbata generally flowers earlier than A. mearnsii (Gowers 1990) A. mearnsii also has darker, green, non-silvery foliage.

    Acacia decurrens (Early Black Wattle) - An introduced species native to NSW is considered an environmental weed in Victoria. A. decurrens branches are angled and its dark green foliage has well separated pinnules (Gowers 1990).

    This description relates to Victoria and may not necessarily apply to other states

     

  1. Did You Know?

    The tannins and gums in the bark of black wattle were used as adhesives by Indigenious people and are also used to tan leather. 

    A. mearnsii plays an important role in Australian 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 the natural regeneration of Australian bushland after fires.

     A. mearnsii is invasive in parts of Asia, southern Europe, southern Africa New Zealand, Cook Islands and parts of USA.

    Alogn with several other Australian species it has the dubious honour of being listedin the top 100 of the world's most invasive species: http://www.iucngisd.org/gisd/speciesname/Acacia+mearnsii.