Two-nerved wattle (Acacia bivenosa)

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Two-nerved wattle fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
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Two-nerved wattle description

The two-nerved wattle (Acacia bivenosa) is a small Australian shrub which normally has a rounded or spreading shape ^{(2) (3) (4)}, sometimes reaching up to three or even six metres across ^{(3) (4)}. It may also occasionally grow flat along the ground, or sometimes be taller and more spindly with drooping branches ^{(3) (5)}. The bark of the two-nerved wattle is grey and smooth ⁽³⁾, sometimes with a whitish, powdery-looking surface ^{(3) (5) (6)}.

As in most other Australian Acacia species, the ‘leaves’ of the two-nerved wattle are actually modified leaf stalks known as phyllodes, which have assumed the form and function of the leaf ⁽³⁾. The phyllodes of the two-nerved wattle are quite variable in appearance, ranging from narrow and oval to egg-shaped or spear-shaped. However, they are usually relatively short and wide, measuring around 2 to 5.5 centimetres in length and 0.6 to 2.5 centimetres in width ^{(3) (5) (6)}.

The phyllodes of the two-nerved wattle are typically quite fleshy and are bluish-green with a slightly powdery-looking surface, or bright green on new growth. The common name of the two-nerved wattle, together with its scientific name, bivenosa, comes from the two nerves, or veins, which normally run down each phyllode ^{(3) (5) (6)}.

The two-nerved wattle’s flowers are golden-yellow ^{(2) (3) (5) (6)} and grow in clusters of around 15 to 25, forming spherical flower heads around 0.5 to 1 centimetres across ^{(3) (5)}. These flower clusters grow on relatively long stalks ^{(3) (5) (6)}. Each of the two-nerved wattle’s flowers has five petals ^{(3) (6)}.

The fruits of the two-nerved wattle are long pods, up to eight or ten centimetres in length, which are light brown and have a hard, brittle texture ^{(3) (6)}. The pods are slightly constricted between the seeds, and readily break at these constrictions to release the glossy seeds, which are oval in shape and dark brown or black with an orange to red tip ^{(3) (5) (6)}.

Also known as

Cable Beach wattle, dune wattle, hill umbrella bush, two nerved wattle, two-veined acacia, two-veined wattle.

Synonyms

Acacia binervosa, Acacia bivenosa var. borealis, Acacia elliptica.

Size

Height: 0.5 - 3 m ⁽²⁾

Two-nerved wattle biology

The two-nerved wattle flowers from April to November ⁽²⁾, with its main flowering period occurring between July and August ⁽³⁾. Its seed pods usually ripen between September and December ⁽³⁾.

This species is usually killed by fire and regenerates from seed, but large individuals may be able to regenerate from the roots after less intense fires ⁽³⁾. The two-nerved wattle is a relatively fast-growing shrub ⁽⁴⁾ and typically has a lifespan of 10 to 30 years ⁽⁵⁾.

Two-nerved wattle range

The two-nerved wattle occurs across arid regions of northern Australia, in western Queensland, the Northern Territory and Western Australia. It also occurs on a number of islands off the coast of Western Australia ^{(3) (6)}.

Two-nerved wattle habitat

The two-nerved wattle grows in a variety of habitats and soil types. For example, this species can be found in coastal sand dunes, rocky hillsides and gullies, shrubland, open stony plains, and open woodland, often with a ground cover of spinifex grass (Triodia wiseana) ^{(3) (6)}. The two-nerved wattle has a preference for well-drained, alkaline soils ^{(3) (4)}, and is tolerant to sea-spray and high levels of salinity ⁽⁵⁾.

Two-nerved wattle status

The two-nerved wattle has yet to be classified by the IUCN.

Two-nerved wattle threats

The two-nerved wattle is not currently considered to be rare or under threat ^{(2) (3)}. This plant has a number of potential uses, including shelter, browse for livestock, agroforestry and stabilisation of sandy soil ^{(3) (4) (5) (7) (8)}, and it has been introduced to other parts of the world for these purposes ^{(7) (8)}. Aboriginal people are also reported to eat the two-nerved wattle’s seeds ⁽⁵⁾, and to obtain edible grubs from its roots ⁽³⁾.

Two-nerved wattle conservation

No specific conservation measures are currently known to be in place for the two-nerved wattle.

Find out more

Find out more about the two-nerved wattle and about other Acacia species:

• Wattles of the Pilbara - Acacia bivenosa:
  http://www.worldwidewattle.com/speciesgallery/descriptions/pilbara/html/bivenosa.htm
• FloraBase: The Western Australian Flora - Acacia bivenosa:
  http://florabase.dec.wa.gov.au/browse/profile/3241
• BBC Nature - Acacias:
  http://www.bbc.co.uk/nature/life/Acacia

More information on plant conservation in Australia:

• The Australian Network for Plant Conservation Inc.:
  http://www.anpc.asn.au/

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Glossary

Agroforestry

A land use system that integrates trees or shrubs into the agricultural landscape and on farms for environmental and human benefit.

Alkaline

Having a pH greater than 7.0. Soil is regarded as alkaline if it has a pH between 8.0 and 10.0. Alkaline soils are usually rich in calcium ions.

References

1. Species 2000 and ITIS Catalogue of Life(April, 2013)
   http://www.catalogueoflife.org/annual-checklist
2. FloraBase: The Western Australian Flora - Acacia bivenosa (April, 2013)
   http://florabase.dec.wa.gov.au/browse/profile/3241
3. Wattles of the Pilbara - Acacia bivenosa (April, 2013)
   http://www.worldwidewattle.com/speciesgallery/descriptions/pilbara/html/bivenosa.htm
4. Nugent, J. and Boniface, J. (2004) Permaculture Plants: A Selection. Permanent Publications, Hampshire, UK.
5. FAO Grassland Species Profiles - Acacia bivenosa (April, 2013)
   http://www.fao.org/ag/AGP/AGPC/doc/GBASE/data/pf000363.htm
6. Orchard, A.E. and Wilson, A.J.G. (Eds.) (2001) Flora of Australia. Volume 11A, Mimosaceae, Acacia Part 1. ABRS/CSIRO Publishing, Melbourne.
7. Wickens, G.E. (1995) Role of Acacia Species in the Rural Economy of Dry Africa and the Near East. Food and Agriculture Organization of the United Nations, Rome.
8. Sandys-Winsch, D.C. and Harris, P.J.C. (1992) Agroforestry and forestry on the Cape Verde Islands. Agroforestry Systems, 19: 79-91.