Botany

Trees of Australia Sheoak



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The sheoak (she-oak) is endemic to Australia.  Sheoaks are actually flowering plants and belong to the genus Allocasuarina  and the family Casuarinaceae.  The sheoak may also be called the ironwood, bull-oak (buloke) or beefwood. The species Allocasuarina luehmannii gives its name to the Shire of Buloke in Victoria, Australia. 

What look like long, drooping, segmented leaves are actually modified branchlets (often called needles). The true leaves are reduced to minute, teeth-like scales which encircle each joint on the branchlets. Groves of sheoak are silent areas. The fallen needles form a soft, dense cover underfoot.  The mat of branchlets stifles any undergrowth. The sheoak bears a woody fruit which looks like a spiny, cylindrical cone, about the size of an acorn, which is flattened at both ends. Sheoak thrive in very poor soils and under semi-arid conditions. The foliage is adapted for droughts and nodules on the roots contain symbiotic nitrogen fixing bacteria. 

Because of its ability to grow in poor and sandy soils, it is often utilised in erosion prone areas or sand dunes to stabilise the soil. It will grow in most locations and is frost resistant.  It forms an excellent windbreak and requires minimal water to get established. Once established, it does not need any further outside assistance but will manage under natural conditions. It is sometimes chosen as a host by the parasitic mistletoe. 

The sheoak has both male and female trees.  Discreet reddish flowers form in winter. The male trees produce large quantities of wind-blown pollen from tiny brown flowers. When in full flower, this causes the tree to take on a rusty red colour. Female trees have flower cones with dark red, thread-like filaments on short, lateral branchlets.  Later, rough cones form from these. Woody bracts on the cone open to release the tiny fruits.  Sheoak trees do not produce nectar. The sheoak is classed as a large shrub or small evergreen tree and the height ranges from 3 to 6 metres tall. The bark is rough and fibrous. 

Sheoaks were known as the aboriginal ‘woman’s tree hence the name she-oak.  Because of the lack of undergrowth, children were encouraged to play in the clear areas under the sheoak as snakes would normally avoid moving over the fallen needles. 

The seed heads are eaten by large parrot species and cockatoos and are the primary food source of the yellow-tailed black cockatoo. Moths and beetles are also attracted to the sheoak thus providing an additional source of food for birds. 

The timber of the sheoak is similar to that of the European oak. It was used, among other things, for roofing shingles. It is popular with furniture makers and wood turners as it is a hard wood with a rich texture and a beautiful, distinctive grain which cannot be mistaken for any other wood. It also makes good burning as it produces very little ash. 

Sources:
www.bankstown.nsw.gov.au
en.wikipedia.org

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