|Allocasuarina decaisneana in Central Australia|
61 species; see text.
Allocasuarina is a genus of trees in the flowering plant family Casuarinaceae. They are endemic to Australia, occurring primarily in the south. Like the closely related genus Casuarina, they are commonly called sheoaks or she-oaks, they are notable for their long, segmented branchlets that function as leaves. Formally termed cladodes, these branchlets somewhat resemble pine needles, although sheoaks are actually flowering plants. The leaves are reduced to minute scales encircling each joint. Fallen cladodes form a dense, soft mat beneath sheoaks, preventing the development of undergrowth (a phenomenon known as allelopathy) and making sheoak woods remarkably quiet.
Another characteristic feature are the spiny "cones", about the size of an acorn but with a texture more resembling a conifer cone. However, sheoak "cones" are actually a woody fruit. Male specimens bear no fruit and are sometimes colloquially referred to as a "heoak".
As with legumes, sheoak roots possess nodules containing symbiotic nitrogen fixing bacteria; together with their highly drought-adapted foliage, this enables sheoaks to thrive in very poor soil and semi-arid areas. However, sheoaks are much less bushfire-tolerant than eucalypts.
Because of its ability to grow and develop extensive root systems in very poor or sandy soils, and to completely cover the ground with its "needles", it is often used to stabilise soils in erosion prone areas, or on sand dunes. Sheoak is also used as an ornamental shrub, although for this purpose the mat of "needles" may become a nuisance and must be carefully considered.
List of species
- Allocasuarina glareicola - endangered species listing Department of Environment & Conservation (NSW). Retrieved 2007-01-23.
- Allocasuarina littoralis www.organicmatters.com.au. Retrieved 2007-01-23.
- Allocasuarina portuensis Department of the Environment and Heritage. Retrieved 2007-01-23.
- Allocasuarina verticillata Windmill Outback Nursery, 2003-03-13. Retrieved 2007-01-23.
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