Heteropogon contortus  (L.) P.Beauv. ex Roem. & Schult. 1817

pronounced: het-er-oh-POH-gon kon-TOR-tuss

(Poaceae —  the grass family)

common name: Black Spear Grass

Heteropogon heteropogon contortuscontortedheteropogon contortusblack spear grassis derived from the Greek 'ετερος (heteros), different, and πωγων (pogon), beard, referring to the awned and awnless spikelets; contortus is Latin for ‘twisted’.

This is a tropical, perennial tussock grass with a native distribution in southern Africa, southern Asia, northern Australia and Oceania. It has also become a naturalized weed in tropical and subtropical regions of the Americas. The plants develop characteristic dark seeds with a single long awn at one end and a sharp spike at the other. The awn becomes twisted when dry and straightens when wet, and in combination with the spike it is capable of drilling the seed into the soil. Although this is a valuable pasture species across much of its range, it has also been responsible for wiping out the wool industry in quite a few parts of Australia, because the seeds become embedded in the wool of the sheep and can work their way into the skin, devaluing the wool and even killing the sheep. The seeds can also have the same effect on dogs with thick undercoats.

Heteropogon contortus grows up to 1.5 m in height, although it is rather variable in habit. Leaves and stems are green to green-blue, and usually hairless or with only a few scattered hairs. The leaf sheath and blade are folded along the midrib and the leaves are anything from 5 to 30 cm long.  The seed heads arise singly or in pairs from the axils of the upper leaves. The spikelets are paired, with one member of each pair being fertile, the other being either male or sterile. The fertile spikelet bears an awn 5–12 cm long, the basal part of which is twisted. The awns of the spikelets in a seed head inter-twine at maturity.

This is a typical species of Australian tropical and sub-tropical tall grass vegetation, growing as an under-storey in eucalypt woodlands and open forest. Plants are largely dormant during the cooler, drier months. Growth begins when both temperature and soil moisture levels are adequate. In the north, low soil moisture limits growth during the dry season, and growth begins with the first major rains. Reproductive development usually beings in early February, and seed is set from late March.

Although black spear grass is seldom cultivated, it grows spontaneously wherever grasslands suffer from seasonal fires. It resists fire very well, and this can lead to the formation of savannahs.

This plant is one of those collected in 1770 by Banks and Solander during the voyage of the Endeavour. It was collected at the Endeavour River (Cooktown).

Photographs taken 2009, Hawkings Point

Page last updated 11th December 2016

 

 

 

 

 

 

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