casuarina

Casuarina is a genus of evergreen trees and shrubs in the family Casuarinaceae, native to Australia, surrounding Indian Ocean islands, and parts of Southeast Asia. Commonly known as casuarinas or she-oaks, they are valued for their slender, columnar shape and feathery foliage.

Morphology and growth

The trees have branchlets that resemble pine needles, with true leaves reduced to tiny scales. The branchlets photosynthesize, giving the plants their distinctive, airy appearance. Flowers are small and inconspicuous; many species are monoecious or dioecious. The fruit is a woody cone containing winged seeds.

Ecology and habitat

Casuarinas are adaptable to poor soils and salt spray, often occupying coastal dunes, riverbanks, and open woodlands. They form actinorhizal root nodules with Frankia bacteria to fix atmospheric nitrogen, improving soil fertility. They provide habitat for birds and various invertebrates. Some species have become invasive outside their native range, where they can outcompete native vegetation and alter local ecosystems.

Uses and management

Wood from Casuarina is light and pale, used for fencing posts, charcoal, and general timber; the trees are also planted for windbreaks, erosion control, and dune stabilization. They are cultivated ornamentally and for reforestation in suitable climates. In regions where they are non-native, management may be required to prevent ecological impacts.

Taxonomy and distribution

The genus includes approximately 17–19 species; it is native primarily to Australia and parts of Asia and the Pacific. Allocasuarina is a closely related genus that has been separated in some classifications. Notable species include Casuarina equisetifolia (Australian pine) and Casuarina glauca (blue-leaf sheoak).