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Coolatai grass (Hyparrhenia hirta)

Coolatai grass is an invasive introduced perennial that has become a major weed in northern New South Wales and southern Queensland, where it can dominate pastures and invade natural areas. It can outcompete native plants, reduce habitat for fauna and create a fire hazard through its large amount of dry growth.

Key facts

Type: Weed, grass.

Native to: South Africa to the Mediterranean region and western Asia.

Established in: QLD, NSW, ACT, VIC, SA, WA.

Other names: Tambookie Grass, Thatching Grass.

Best time to act: Coolatai grass grows and flowers from late spring to autumn when moisture is adequate, and herbicide spot treatment is useful before seed set.

Identification

  • A tall, densely tufted perennial grass, usually reaching 1.2 to 1.5 metres in height.
  • Its rough leaves are grey-green to blue-green and have a waxy bloom that can be rubbed off.
  • Loose, sparse flower heads have paired branches with numerous flowers forming V shapes at the ends.
  • Each spikelet has a golden-brown awn about 1.5 to 2.5 centimetres long, with a hairy base.
  • Look-alike: Native Tambookie grass (Hyparrhenia filipendula) has 1 to 3 awns per spikelet, and its awns are 4 to 5 centimetres long.
  • Look-alike: Jaragua grass (Hyparrhenia rufa) has 9 or 10 awns per raceme, each 16 to 22 millimetres long.

Where it grows

In Australia it occurs in all mainland states and territories, especially across western, central and coastal New South Wales, and grows in pastures and open woodlands and grasslands on a wide range of soils.

Why it matters

  • It can dominate pastures, particularly where ground cover is low, and older growth is avoided by stock.
  • In natural areas it outcompetes native plants, prevents their regeneration and reduces available fauna habitat.
  • Large amounts of dry growth create a fire hazard and can alter fire regimes.
  • It invades roadsides, railway lines, urban fringes and other disturbed or degraded sites.

How it spreads

  • Seeds are carried in hairy, awned husks that stick to clothing, animals and vehicles.
  • Slashing, mowing, traffic and water movement can spread seed, especially along roadsides.
  • It can self-pollinate and produce many seeds from one plant.

Control options

  • Map infestations and direct early control efforts to lightly infested areas, working back toward heavier infestations.
  • Small infestations can be grubbed out; combining physical treatment such as chipping with registered herbicides can help, as herbicide alone may not kill mature tussocks.
  • Follow up after treatment, as seedlings may appear for several years after tussocks are sprayed; burning or mowing alone may spread an infestation or make it denser.

Hygiene and washdown

  • Remove grass trash and seed from slashers and graders before moving from infested to uninfested areas.
  • Check and clean clothing and vehicles because the hairy seed husks can stick to them.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Regional priority in 5 of 11 regions. Regional priority weed in Central Tablelands, Central West, Murray, Riverina, Western. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Not declared. Not declared under the Catchment and Land Protection Act 1994. Other Victorian laws may still apply.
  • South Australia: Declared plant. Depending on the declaration, it can be an offence to move it on public roads or sell it, and landowners may be required to control it on their land.
  • Western Australia: Permitted, not declared. Listed as a permitted organism in WA, so it can be brought in, but it is not a declared pest.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Not declared. Not on the NT A to Z weed list, and Weeds Australia does not list it as declared in the NT. Check the NT declared weeds list before moving or planting it.
  • Australian Capital Territory: Declared pest, notifiable, prohibited. It is a declared pest throughout the ACT. You must report it to ACT Biosecurity. Dealing with it, such as selling, moving or keeping it, is prohibited.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)
  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • Australian Capital Territory: Biosecurity Act 2023 (ACT), administered by ACT Biosecurity
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources