The Swamp Oak is October's plant of the month.
Casuarina glauca grows along the east coast of Australia, from central Queensland, down to southern NSW. It is limited in its natural distribution to moist areas, alongside watercourses, estuaries and coastal areas. It has, however, been planted as a street tree throughout NSW and the ACT.
Casuarina glauca suckers from the roots and this means it grows in dense, often single species stands, and can crowd out other species. It grows readily in waterlogged soils where the watertable is around 300mm from the surface and colonises stream edges and coastal zones, especially along estuaries and can act as a coloniser species, allowing soil to build up around the dense root mats.
There are six species of Casuarina and 59 species of Allocasuarina. They are commonly called she-oaks because the timber is similar to the European oaks.
Casuarina foliage typically comprises numerous slender, wire-like, jointed, photosynthetic branchlets that droop from the tree’s branches. The leaves themselves are reduced to tiny scales surrounding the branchlets. The fruit is a woody, oval structure superficially resembling a conifer cone. The seeds are winged to allow for wind pollination.
Casuarina glauca is a tree, growing to 30m, however depending on local conditions it can be stunted or dwarfed and even grows as a prostrate form.
Casuarinas can fix nitrogen, which is an essential nutrient for plant growth. This process depends on symbiotic bacteria that live in the plant’s root system. Nitrogen fixation provides an additional nitrogen source for wider forest ecosystems.
Casuarina glauca, and the closely related river she-oak (Casuarina cunninghamiana), grow along river and stream banks. Their roots help stabilise the banks, which reduces surface-water runoff, erosion and sedimentation. This helps maintain water quality for environmental and recreational purposes.
Casuarina wood is dense and very hard, which makes it an excellent fuelwood. Indigenous Australians have traditionally used the wood for shields, clubs and boomerangs.
In colonial times, wood from various species was used for roof shingles, fencing, handles and bullock yokes. Timber from some casuarinas has an attractive, wide, dark-coloured grain and is used for wood-turning, small cabinetwork and parquetry.
Where to see Swamp Oak in Centennial Parklands
Guriwal Bush Tucker Trail, Lachlan Swamp, roadside and parkland plantings.