T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Casuarina glauca (Swamp oak)

Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Fagales
Family: Casuarinaceae
Genus: Casuarina
Species: C. glauca
Binomial name: Casuarina glauca
Synonym: Casuarina obtusa
Common name: Swamp oak; Swamp she-oak, Grey oak, River oak, Brazilian oak, cadigal, gray sheoak, grey she-oak, guman, long-leaf ironwood, longleaf ironwood, saltmarsh ironwood, scaly-bark beefwood, swamp she oak, swamp she-oak, swamp sheoak, swamp oak.

Casuarina glauca is a coastal species of Casuarina native to the east coast of Australia. It is a tree up to 20 m tall with a well-developed lateral root system, which often forms vigorous root suckers. C. glauca is a dicotyledonous, actinorhizal, angiosperm having an ability to form a symbiosis with the nitrogen fixing actinobacteria Frankia. This association leads to the formation of nitrogen-fixing root nodules.
The trunk's rough bark is grey to light brown in colour and is frequently colonised by patches of lichen. The tree has slender often drooping branches with branchlets that have between 12-16 tiny scale like leaves per segment.
Clusters of rusty coloured male flower and red female flowers appear during August and September. Many small cone-like seed pods occur directly on branches of the female trees and persist on trees for at least one season. The seeds are winged seeds and can start to germinate in about 5 days.

Casuarina glauca has become naturalised in New Zealand and because of its ability to produce root suckers which in turn grow into new trees or forming clumps which out compete adjacent plants it now considered a weed. This species often fringes estuaries and is usually found on alluvial, acidic soils that are saline.

At a distance Casuarina glauca looks like a pine and it may be confused with young Dacrycarpus dacrydioides (kahikatea). The trees in photos below were photographed on the the Collingwood Popunga Coastal Road, Golden Bay, South Island, New Zealand.


Small tree.


Coastal roadside plants.


Female cones.




Photo of cones on female tree. Photo courtesy of Forest & Kim Starr ,Wikinedia Commons