Xanthorrhoea australis)

Appearance

The main way to identify ''Xanthorrhoea'' is by looking at the cross-section of the leaves. In the case of ''X. australis'' the cross-section is a rough diamond shape, and the colour of the leaves is a bluish-green.

The species usually develops a rough trunk which may be branched and coloured black, the result of bushfires. The trunk is able to grow up to over 3 metres in height with a width of up to 1 metre and may be branched. The bark is thick, rough and corky. The plant is very slow growing and trunks only start appearing after many years. The long, narrow leaves are crowded together at the tops of the trunks.

''X. australis'' takes several years to flower, and it does not always flower annually, but in the season after a bushfire it flowers prolifically. The flowers appear on a spear-like spike which can grow up to 2 metres tall. The flowers, with 6 petals, usually cover 1⁄2–5⁄6 of the stem.

The crown of leaves is almost spherical in shape, the point of each leaf perfectly marking the shape of the imagined sphere. The leaves crown the trunk in a crowded whorl of long, wiry leaves. They are arranged in a spiral, forming an erect tuft when young and spreading as they mature, with the oldest leaves dying and forming a hanging skirt around the trunk. The blue-green needle-like leaves are typically 14 to 30 centimetres long and have a waxy coating. The leaves are softer and generally less rigid than other Xanthorrhoeas. Old leaves hang down forming a distinctive skirt-like feature that partly covers the fire-blackened trunk. ''X. australis'' flowers from July to December, but younger plants may flower in June.

The common name ''grass tree'' is accurate as the trunks and branches of the tree varieties are literally made out of the leaf bases, not wood.

Grass trees are often very long-lived with some estimated to be 350 to 450 years old.

Distribution

This species can be found in the states of New South Wales, Australian Capital Territory, South Australia, Western Australia, Tasmania and Victoria. It is regarded as the most widely distributed all of the ''Xanthorroea'' species. It is able to survive in poor soils, is intolerant to phosphorus and is highly susceptible to the soil-borne disease ''Phytophthora cinnamomi''.

Uses

Indigenous Australians soaked the flowering spikes in water to produce a sweet drink. The soft, white leaf bases were eaten as well as the growing point of the stem. The flower spike exudes a resin which could be used as an adhesive in the manufacture of tools and the stem used for the lower portion of a spear. Stems were also used to make a base for a fire-drill to start a fire.
The resin was also collected and sent to commercial processors where it was made into lacquer for furniture of cabinet makers.

In 1915 there was considerable consternation over the realisation that German agents had been buying “''immense quantities of grass tree gum for the past quarter of a century''”, presumably for the purpose of manufacturing explosives. The explosive containing grass tree resin was reported as more explosive than dynamite in experiments at the time.