Quick Facts

Quick facts

• Grader Grass (Themeda quadrivalvis) is a robust, but short-lived, tufted grass that grows up to 2 m tall.
• It grows rapidly and produces several upright flowering stems that turn reddish-brown or golden-brown as they mature. In perfect conditions flowers are produced only 5–6 weeks after germination and mature seeds can be set 10 weeks after germination.
• Grader Grass is a common and widespread weed of roadsides, pastures, and native grasslands in the tropical and semi-arid regions of northern Australia.
• It can significantly reduce the productivity of native and sown pastures, and is also an important weed of sugar cane crops.
• Grader Grass can also significantly reduce the biodiversity of native grasslands, savanna woodlands and rangelands. It alters the fire regime in these communities and can transform native savanna woodlands into exotic grasslands.

What Does It Look Like?

What is it?

Grader Grass (Themeda quadrivalvis) is a robust, but short-lived, tufted grass that usually grows 50 cm to 2 m tall. Plants produce several hairless upright stems from each rootstock. These stems (4–6 mm thick) are green at first, but turn reddish-brown or golden-brown in colour as they mature. The alternately arranged leaves consist of a leaf sheath, which partially encloses the stem, and a long and narrow leaf blade (7–60 cm long and 1–7 mm wide). These leaves are folded in the bud and green at first, but turn brown or reddish-brown in colour with age. The leaf blades are flat, or their margins are sometimes rolled under, and they have pointed tips. Where the leaf sheath meets the leaf blade there is a small membranous structure (a ligule) 1–3 mm long (Navie & Adkins 2007).

The seed-heads (15–60 cm long) have several small branches that are interspersed with leafy bracts. They turn brown or slightly reddish in colour and become somewhat drooping in nature as they mature. These seed-heads consist of several complex triangular or fan-shaped flower clusters (1–3 cm long), enclosed in leafy bracts (about 2 cm long), that contain both fertile and sterile flower spikelets. The fertile flower spikelets (5–6 mm long) are oval or almost cylindrical in shape. They consist of one tiny fertile flower, one tiny sterile flower and a pair of bracts (known as glumes) at the base. The glumes (4.5–6 mm long) are elongated in shape and stiffly hairy in their upper parts. The seeds (4.5–5.5 mm long) are brown in colour with an obvious cluster of reddish hairs at the base. They are topped with a relatively large, bent and twisted, awn (10–45 mm long) and are enclosed within two hairless floral bracts (Navie & Adkins 2007).

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

Flower colour

Green

Growth form (weed type/habit)

Grass

Where it currently grows? Preferred habitat

Grader Grass is a weed of roadsides, disturbed sites, waste areas, open woodlands, grasslands, pastures and crops that is mainly found in tropical and subtropical regions (Navie & Adkins 2007).

Are there similar species?

Grader Grass is very similar to several closely related native grasses, including Kangaroo Grass (Themeda triandra), Native Oatgrass (T. avenacea) and Lesser Tanglegrass (T. arguens).

Kangaroo Grass is a longer-lived plant that usually only grows to about 1 m tall. Its flower spikelets are larger (6–14 mm long) and are not very hairy. Native Oatgrass does grow to the same height, but is also longer-lived and has much larger hairy flower spikelets (13–30 mm long). Lesser Tanglegrass is short-lived like Grader Grass, but grows up to 3 m tall and has longer, softly hairy flower spikelets (6–11 mm long) (Navie & Adkins 2007).

Why Is It A Weed?

What are its impacts?

Grader Grass was included in the list of 71 species that were nominated by state and territory governments for assessment as Weeds of National Significance (WONS). Following an assessment process, Grader Grass was not included as one of the 20 WONS. However, it remains a weed of potential national significance.

Agriculture: Younger plants are readily eaten by livestock, but flowering plants are unpalatable and rarely grazed. Because of its short period of usefulness, and propensity to out-compete more useful grasses, Grader Grass can seriously reduce the productivity of pastures in the tropical and semi-arid regions of northern Australia. It is also an important weed of crops in many parts of northern Australia, and is particularly troublesome in sugar cane (Parsons & Cuthbertson 2001). It is regarded as a major crop weed in coastal northern and central Queensland, and a minor crop weed in inland central Queensland and the Northern Territory (Wilson et al. 1995). Grader Grass is also a very common weed of roadsides, where it can quickly become a safety hazard by reducing visibility on corners (Parsons & Cuthbertson 2001).

Native ecosystems: Grader Grass can also significantly reduce the biodiversity of native grasslands, savanna woodlands and rangelands, particularly in areas that are overgrazed or disturbed (Smith 2002). It replaces native plants and forms tall thickets that can cover large tracts of land. Due to its greater biomass than the native plants it replaces, and hence its higher fuel loads, Grader Grass alters the fire regime. It does this by carrying more wildfires that are of a much greater intensity than the native plants are used to. Each of these hot fires, during the late dry season, cause a thinning of the native woodlands and eventually the number of trees in the ecosystem are reduced, resulting in a change from native savanna woodlands to exotic grasslands (Navie & Adkins 2007).

For these reasons Grader Grass is also seen as an important environmental weed in northern and eastern Australia. It is currently causing most concern in the semi-arid rangelands of northern Queensland and the Northern Territory, where it is abundant and continuing to spread. However, it also appears in the list of the top 200 most invasive plants of south-eastern Queensland, is in the New South Wales North Coast environmental weed list, and was recently listed as a priority environmental weed in two Natural Resource Management regions. It is also seen as a potentially significant threat to the Kimberley region in northern Western Australia, though it is not yet very widespread in this region (Batianoff & Butler 2002; Navie & Adkins 2007).

How does it spread?

Grader Grass seeds are spread by animals and vehicles, in clothing and mud, and as a contaminant of agricultural produce. They are also commonly dispersed during soil moving activities, such as the grading of roads, hence the name "Grader Grass" (Parsons & Cuthbertson 2001; Navie & Adkins 2007).

What is its history in Australia?

Grader Grass was first recorded in Australia in 1935 at Habana, near Mackay, in central Queensland. It is thought to have been introduced accidentally as a contaminant of pasture grass seed from India. It has since spread along the eastern coast of Australia, from Cairns to northern New South Wales, and has also been accidentally introduced into the Northern Territory as a contaminant of pasture grass seed from Queensland (Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

Non-chemical control: Grader Grass should first and foremost be prevented from entering uninfested properties. If improved pastures are being sown, ensure that the pasture seed does not contain any Grader Grass seeds, as contaminated pasture seeds are the most common means of spread of this species to new areas. If Grader Grass is already present on your property, you should be careful not to spread it to clean areas on contaminated vehicles, machinery or livestock (Pitt 1998; Parsons & Cuthbertson 2001).

Manual control: Small infestations should be hand-pulled or dug out and burnt on site, preferably before seeding. Alternately they can be controlled by spot spraying with a recommended herbicide. Larger infestations often require a combination of improved pasture management and, where the weed is growing above the pasture, the application of herbicides through a pressure rope-wick applicator. Care should be taken to avoid overgrazing, short slashing or burning of pastures and these actions will give Grader Grass an advantage over other species (Pitt 1998; Parsons & Cuthbertson 2001).

Dense infestations of Grader Grass can be slashed prior to seed set; however, the plant has the ability to send up new seed-heads from slashed plants if conditions are favourable. In heavily infested areas, re-sowing the pasture is sometimes the best option. This should be done during the wet season, after the area has been cultivated at the end of the previous wet season, prior to the production of seed-heads (Pitt 1998; Parsons & Cuthbertson 2001).

Chemical control: In cropping areas, roadsides and nearby headlands should be kept free of Grader Grass to prevent it spreading into nearby crops. Within crops, Grader Grass can be controlled by inter-row cultivation or by application of an appropriate herbicide (Parsons & Cuthbertson 2001).

Check with your local council or state/territory government agency about its requirements for the control of Grader Grass. Also see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au .

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Grader Grass seeds can germinate at any time of the year when adequate light and moisture are available. In northern Australia, most seeds germinate with the onset of the wet season (between October and December). Growth is very rapid and plants can reach a height of 2 m in 6–8 weeks (Parsons & Cuthbertson 2001). Flowering occurs mainly during summer and autumn, but may also occur during winter (Navie & Adkins 2007). In good growing conditions these flowers begin to be produced only 5–6 weeks after germination and mature seeds can be present only 4–5 weeks later (Parsons & Cuthbertson 2001).

Where Is It Found?

Which states and territories is it found?

NSW, NT, QLD, WA

What areas within states and territories is it found?

Grader Grass is widely naturalised throughout the coastal and sub-coastal regions of the Northern Territory and Queensland. Scattered populations are also found in the northern parts of Western Australia and in the coastal districts of northern New South Wales (Navie & Adkins 2007).

Where does it originate?

Grader Grass is native to the Indian sub-continent (India and Nepal) and possibly also parts of south-eastern Asia (Thailand, Vietnam, Myanmar and Indonesia) (GRIN 2007; Navie & Adkins 2007).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NT

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Themeda quadrivalvis

Other scientific names (synonyms)?

• Andropogon quadrivalvis L.
• Anthistiria ciliata L.f.
• Themeda ciliata (L.f.) Hack.

Does it have other known common name(s)?

Habana Grass, Kangaroo Grass, Oatgrass