Form: grass - annual
Status: present in WA
Native to India and Nepal, grader grass is an upright, tufted annual grass. This species is found in North and South America, New Caledonia, Fiji, Mauritius, Thailand, Indonesia, Papua New Guinea, China and the Middle East. In Australia, grader grass occurs throughout the coastal and sub-coastal regions of the Northern Territory and Queensland, the coastal districts of northern New South Wales and in the northern parts of Western Australia.
In WA, it is found in the central and northern Kimberley region and is particularly prevalent in locations along on the Gibb River and Kalumburu Roads. It appears to be present on most other roads and tracks within the North Kimberly.
Grader grass is an erect tufted grass that grows 0.5-2m tall, usually about 1.2m. As the plant matures, it turns reddish-brown or golden-brown in colour. It has robust, cane-like stems with long complex seed heads.
This plant can be confused with native kangaroo grass (Themeda triandra) and possibly native oatgrass (Themeda avenacea).
Leaves: folded leaf-blades 7–60cm long, 1–6mm wide are arranged alternately along the stem. The leaf margins are flat or sometimes rolled under and the leaf blades have pointed tips.
Stems: cylindrical and hairless stems, 4–6mm in diameter, 5-7 nodes.
Flowers: the seed heads consist of several complex triangular-shaped or fan-shaped flower clusters (1-3cm long), enclosed in leafy bracts (about 2cm long), that contain both fertile and sterile flower spikelets. Spikelets have bent, brown bristles at the ends and are surrounded by leafy bracts with dense clusters of hairs. The fertile flower spikelets (5-6 mm long) are oval or almost cylindrical in shape. Flowering generally occurs in February to June in Australia. Flowers are usually produced within 5 to 6 weeks after germination
Seeds: seeds can be produced within ten weeks of flowering. However, germination can occur throughout the year if there is adequate moisture. Grader grass can produce up to 1000 seeds in a single seed head. Grass dies when seeds are mature. Seeds last up to four years in soil.
This plant only reproduces by seed. Seeds are usually dispersed during soil moving activities, such as the grading of roads (hence the common name ‘grader grass’), the moving of plant material on slashers, or as a contaminant in pasture seed or hay. Seeds are spread in animal fur; on clothing, vehicles and mud; and as a contaminant of agricultural produce.
Agricultural and economic impact
Grader grass is a weed of open native woodlands and grasslands, significantly reducing species diversity. It is found in disturbed areas, waste areas, roadsides, railway embankments, and in sugarcane, pasture, lucerne and legume seed crops, in tropical and sub-tropical regions.
Grader grass entered the Kimberley mixed in with stock feeds and pasture seeds. It then colonised disturbed areas around cattle yards, bores and where cropping was undertaken. This grass can yield more than 5000 kg/ha after one growing season, outcompeting native and sown pastures and grasses by reducing plant productivity. Because it has low palatability, it can reduce livestock productivity if it becomes dominant in pastures.
Declared pest category
The Western Australian Organism List (WAOL) contains information on the area(s) in which this pest is declared and the control and keeping categories to which it has been assigned in Western Australia (WA). Search for grader grass in the WAOL using the scientific name Themeda quadrivalvis.
Requirements for land owners/occupiers and other persons
Land owners/occupiers should refer to declared plant requirements if grader grass is found on their property.
Search > detect > report
Pest and Disease Information Service (PaDIS)
Control methods for this declared plant can be found through the grader grass control link.
Small infestations should be controlled manually, preferably before seeding. For more information refer to the Kimberley Grader Grass Action Plan.