Necklace sheoak

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 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.

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.