River She-Oak, Casuarina cunninghamiana

Adult height: 20-35m

Photo credit: Kenpai

Description: Australian native, similar to a pine in appearance, makes excellent shelter belt, very hardy, good firewood This particular variety of casusarina not only makes an attractive specimen tree, it is also incredibly useful as a shelter belt. It proved one of the most effective shelter trees during 1988s Cyclone Bola, which caused extensive damage to trees in the northern half of the North Island.

While it’s not as fast growing as it is in its native Australia, it has been used extensively by New Zealand orchardists for wind protection. It grows in just about any soil - dry, wet, alkaline, saline, desert and even on coastal properties, although obviously you will get faster growth on more fertile soils.

While it is known around the world for its nitrogen-fixing properties, research has shown New Zealand’s colder soil temperatures inhibits this ability in trees growing here.

Photo credit: Kenpai

The small sapling will need protection from grazing animals, rabbits and hare when small and rats have been known to ring-bark them. It takes off to form a pyramid-like shape in its younger years but eventually forms a more open tree as it ages. It is incredibly tolerant of being brutally pruned and when planted in a shelter situation, will happily rebound after having its head lopped off, to form a tall windbreak. It also tends to keep its lower growing branches close to the ground, although severe pruning will damage its ability to regrow these if you get too carried away.

It is wind and drought tolerant but doesn’t do as well in poorer soils as it does in its native habitat where it is known for its incredibly fast growth. In Australia it is a protected native tree and used to control erosion along stream banks and for revegetation purposes on sand dunes.

The tiny cones the tree drops are full of seed and they will reproduce very easily. In the US the tree has become a pest in some parts of the country because seed has blown into native bush and the young trees compete vigorously so bear this in mind if you are planting stands of native bush.
The male flowers are carried on the ends of branches and as the pollen ripens, the whole trees turns brown, causing people to think their tree is dying or diseased.
If you get sick of your casuarinas (and it’s profuse dropping of needles and tiny pine cones might mean you do resent it a little) it makes brilliant firewood either green or dried and leaves little ash afterwards. While it’s a slow grower here compared to Australia, it still measures up quite well compared to other good firewood trees.

Casuarina cunninghamiana’s foliage is palatable to stock and while they’ll probably happily munch on it, it’s not as all-round a fodder as poplar or willow.

Sister species Casuarina glauca is also useful on the farm – it likes high soil moisture and salt concentrations, making it suitable for use in biomass plantations for effluent disposal. Other uses could include estuarine bank protection, sand dune revegetation, farm windbreaks, and hillside stabilisation plantings.

Nadene Hall
NZ Lifestyle Block magazine