Casuarina glauca aka Brazilian Oak

Casuarina glauca is an evergreen tree in the Casuarinaceae family. Swamp oak and grey she-oak are two common names. It comes from eastern Australia, including Queensland and New South Wales. Useful Tropical Plants also lists Victoria within its range. It grows near saltwater estuaries and along slow creeks. It also occurs on higher ground near these wet sites. In some places, it forms open woods with few other trees.

The tree reaches about 59 feet (18 metres) in height. Its trunk can reach about 2 feet (0.6 metres) across. Useful Tropical Plants describes its growth as moderately fast. It keeps its foliage throughout the year and can fix nitrogen. PFAF reports male and female flowers on the same plant. The tree bears seed cones. Root suckers help it spread beyond the main trunk. This growth can make a dense windbreak, but it also creates problems.

Grow it in full sun, not shade. PFAF recommends soil that holds moisture but drains well. Sandy and loamy soils suit it, though it accepts many garden soils. It tolerates acid and alkaline ground, with a reported pH range of 5–8. It can also cope with salt in the soil and waterlogged ground. PFAF gives mixed reports about its tolerance of coastal exposure. Its cold limits also vary between accounts. Some reports place the limit near 27°F (-3°C). Others record survival near 19°F (-7°C) in Australian gardens. PFAF lists USDA zones 8–11.

People plant swamp oak for shelter and to restore damaged land. Its roots help hold soil on eroded slopes. The tough wood serves for tool handles, fence rails, poles, and shingles. Other uses include saltwater pilings, charcoal, and fuel. Its ability to spread needs care when choosing a site. PFAF reports that it has become a serious weed in some places. Some parts of Florida have banned its planting. Growers have used ditches beside shelterbelts to limit root suckers.

PFAF lists leaves as an edible part, with limited food value. It reports that people chew the needle-like growth to ease thirst. That source notes some doubt about which plant part the report means. It lists no known medicinal use. Both PFAF and Useful Tropical Plants flag a possible pollen allergy risk.