Weeds in Australia


Piptochaetium montevidense


Uruguayan Rice Grass (Piptochaetium montevidense) is a long-lived tussock-forming grass usually growing 0.3 to 0.6 m tall. Its stems are generally unbranched and hairless. The leaves consist of a sheath, which partially encloses the stem, and a spreading leaf blade. They are tufted together at the base of the plant and alternately arranged along the upright flowering stems. Where the leaf sheath meets the leaf blade there is a tiny membranous structure (ligule) 0.5 to 2 mm long. The leaf blades, 50 to 150 mm long and 0.5 to 1 mm wide, are very narrow and are usually folded or rolled inwards. They have hairless or slightly hairy surfaces (Sharp & Simon 2002; Navie & Adkins 2007).

The plant has a branched flowering head, 2 to 100 mm long and 10 to 20 mm wide, but the branches are relatively short and held close to the main stem. Each of the seed-head branches bears numerous small flower spikelets on individual stalks. These flower spikelets, 3 to 3.5 mm long, consist of a pair of bracts (glumes) and a single tiny flower. They are oblong in shape, flattened and purplish in colour when young. The seed, which is about 2 mm long, is topped with a relatively short, up to 10 mm long, bristle-like tail (the awn) (Sharp & Simon 2002; Navie & Adkins 2007).

For further information and assistance with identification of Uruguayan Rice Grass contact the herbarium in your state or territory.


Uruguayan Rice Grass is only known to have become naturalised at Cherry Lake, in Altona, in southern Victoria (McLaren et al. 2004). However, it has been estimated to have a potential distribution of 600 000 hectares throughout Victoria and New South Wales, and may also have the potential to invade parts of South Australia, south-western Western Australia and eastern Queensland (McLaren et al. 2004).

Key points:
  • Uruguayan Rice Grass (Piptochaetium montevidense) is a long-lived tussock-forming grass usually growing 0.3 to 0.6 m tall.
  • It is closely related to several other South American stipoid grasses that have become significant environmental and economic weeds in Australia.
  • So far, Uruguayan Rice Grass has only been found at one location in Victoria.
  • It been identified as a priority for eradication by the Bureau of Rural Sciences (BRS), Canberra, because of the threat it poses.
  • Any new outbreaks should be reported to your local council or state or territory weed management agency. Do not attempt control on your own.
How it spreads:

The seeds of this species are dispersed by wind and also by grazing animals ingesting the plant and depositing the viable seed elsewhere. They may also be spread in contaminated soil and agricultural produce. Anecdotal evidence suggests that seeds are not carried or dispersed externally by stock (CRC 2003).

Where it grows:

In its native range Uruguayan Rice Grass frequently grows along rivers, in grasslands and in rocky sites (Cialdella & Giussani 2002). Evidence from other parts of the world suggests that this species will grow in crops, along roads and streambanks, and in natural environments such as grassy woodlands and lowland grasslands. In Australia it has been recorded growing in grasslands along with native grasses (CRC 2003).

Flower colour:Green
Distribution map: Weed Distribution Map

Uruguayan Rice Grass is on the Alert List for Environmental Weeds, a list of 28 non-native plants that threaten biodiversity and cause other environmental damage. Although only in the early stages of establishment, these weeds have the potential to seriously degrade Australia's ecosystems (CRC 2003).

Because Uruguayan Rice Grass forms dense tussocks, is stimulated by fire and is resistant to grazing, this species may have the ability to out-compete native plants, especially in disturbed or heavily grazed areas, and reduce the productivity of pastures. Uruguayan Rice Grass is closely related to several other South American stipoid grasses that have become significant environmental and economic weeds in Australia (e.g. Nassella spp.). For example, serrated tussock (Nassella trichotoma) costs south-eastern Australia's grazing industries more than $40 million a year in lost production and control expenditure (CRC 2003).


Uruguayan Rice Grass is native to southern Brazil, Ecuador, Venezuela, Bolivia, Peru, Argentina, Chile, Uruguay and Paraguay in South America (Cialdella & Giussani 2002).


It is not known how Uruguayan Rice Grass was introduced to Australia. This species was recorded from a single location near Melbourne in 1988. However, this lone population appears to have been accidentally eradicated when it was covered by landfill (CRC 2003).


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