Swamp She-oak - profile

Indicative distribution


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Key:
known
predicted
The areas shown in pink and/purple are the sub-regions where the species or community is known or predicted to occur. They may not occur thoughout the sub-region but may be restricted to certain areas. ( click here to see geographic restrictions). The information presented in this map is only indicative and may contain errors and omissions.
Scientific name: Casuarina obesa
Conservation status in NSW: Endangered
Commonwealth status: Not listed
Profile last updated: 20 May 2014

Description

The Swamp She-oak is a much-branched shrub or small tree, 3 to 15 metres tall (though most plants in NSW are less than 8 metres), with deeply-fissured, corky bark. The branchlets are up to 30 centimetres long and 2 to 3 millimetres in diameter, with the leaves reduced to about 16 minute teeth that circle each joint. Each segment between the slightly spreading teeth are 8 to 14 millimetres long. The flowers are small, the male ones are produced in a dense spike 5 to 6 centimetres long on the ends of the branchlets. The fruits are clustered in a cone 10 to 20 millimetres long.

Distribution

The Swamp She-oak is widespread in southern Western Australia and plants from this population are widely planted (including in NSW) for agroforestry, particularly in salt-effected areas, and as a street tree. The eastern population is much more restricted with only scattered occurrence in the Wimmera and Mallee in Victoria, and one occurrence, at Lake Benanee in New South Wales. The NSW population, consisting of only male plants was first discovered in 1951, but was believed to have been cleared prior to 1979 (and hence considered extinct in NSW). In 1999, it was confirmed to still occur at the site, although as all plants are females it is believed this is a different population. The plants occur at three discrete locations along just over a kilometre of the north-western shoreline of the lake, to the south west of the original population.
A recent record from near Moama in the South West Plains Botanic Division has not been confirmed.

Habitat and ecology

  • Requires moist, slightly saline soils. Potential habitats include shorelines of permanent, ephemeral or relict lakes. These systems may be freshwater or saline-influenced judging by the present distribution of the species.
  • In NSW, associated species include River Red Gum (Eucalyptus camaldulensis), Black Box (E. largiflorens) and River Cooba (Acacia stenophylla) with the understorey dominated by grasses and sedges.
  • Flowering time is not known in NSW. Flowers are seldom seen in Victorian populations but have been recorded throughout the year in Western Australia.
  • Recent surveys at Lake Benanee populations report suckering of Casuarina obesa (although suckers were heavily browsed by stock, rabbits and kangaroos).
  • Seedlings of Casuarina obesa in Western Australia have been found to be highly tolerant of saline waterlogged conditions.
  • Plants can develop an unusual thickness of the branchlets and exceptionally large fruits, characters that are due to insect and fungal infection affecting particular stands. NSW populations have also recently suffered from borer attack, possibly associated with drought conditions in recent years.
  • Segregation of male and female stands of the species occurs.
  • Population sizes across the range of the species vary from one plant to over 200 trees scattered in groups of three to six; has been observed growing in extensive thickets; some trees are very old and apparently healthy.

Regional distribution and habitat

Click on a region below to view detailed distribution, habitat and vegetation information.


Threats

Recovery strategies

Activities to assist this species

Information sources

CMA CMA sub-region Known or predicted Geographic restrictions region
Lower Murray-DarlingRobinvale Plains (Part C) Known None