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Mission grass (Cenchrus polystachios)

Mission Grass invades crops, pastures, roadsides and native plant communities in northern Australia, where it can reduce crop yields and replace native species. Its heavy dry growth creates a high fuel load, contributing to extremely hot fires that can kill trees and transform savanna into exotic grassland.

Key facts

Type: Weed, grass.

Native to: Tropical and subtropical Africa, possibly also tropical Asia..

Established in: QLD, NT.

Other names: Perennial Mission Grass, Missiongrass, Feathery Pennisetum, Feather Pennisetum.

Best time to act: Look for actively growing plants and treat before seeding; flowering is mainly from late summer to early winter, and the main seeding period is April to June.

Identification

  • A large, long-lived tussock-forming grass, usually 2–3 m tall, with several hairless flowering stems rising from the plant base.
  • The long, narrow leaf blades are 5–45 cm long and 3–18 mm wide, and may be hairless or somewhat hairy near the base.
  • Upright or slightly drooping, spike-like seed-heads are 3–35 cm long and 6–26 mm across, and are usually yellowish-green to brown, mostly yellow.
  • Each small flower spikelet is surrounded by feathery bristles, with one bristle much longer than the others; mature seed-heads turn yellowish-brown or straw-coloured.
  • Look-alike: Similar grasses include African Feather Grass, Annual Mission Grass, Elephant Grass, Buffel Grass and South African Pigeon Grass.
  • Look-alike: Annual Mission Grass, also called Deenanth grass, has purplish seed-heads and is shorter-lived; Mission Grass is robust and usually has yellowish or brownish seed-heads.

Where it grows

In Australia it is widely naturalised in northern and eastern regions, especially northern parts of the Northern Territory and northern Queensland, and grows along roadsides and in disturbed areas, grasslands, open woodlands, forests, crops and pastures.

Why it matters

  • In the Northern Territory it has been reported to reduce the yield of summer crops such as sorghum, maize and cotton, and the viability of sown pastures.
  • It competes with short-lived grasses and replaces native species, reducing biodiversity and the richness and abundance of native species in savanna woodlands.
  • Its robust growth dries off each year and creates a very high fuel load, leading to extremely hot late dry-season fires that can carry flames into tree canopies and kill trees.
  • Its invasion can transform natural savannas into exotic grasslands and reduce habitat quality for native animals, including the endangered Yellow-snouted Ground Gecko.

How it spreads

  • Mission Grass generally reproduces by seed; its light, fluffy seeds are dispersed by wind and water.
  • Seeds may attach to animals, clothing and vehicles, or be spread as contaminants in agricultural produce such as hay and grain.

Control options

  • Aim to restrict its spread, prevent entry into clean areas, reduce fire hazard and limit competition in crops and pastures; small infestations can be hand-pulled or dug out with a hoe.
  • In cultivation, mature plants can be ploughed in before planting; cultivation combined with registered herbicides usually gives the best results, while pasture management can combine registered herbicides with grazing management.
  • Apply registered herbicides to actively growing plants before seeding; spot sprays suit new or light infestations, while rope wicks and boom sprayers are more applicable to larger, denser infestations.
  • Slashing before seeds mature can lessen fire hazard, but avoid spreading mature seeds with machinery and use fire carefully because it can promote invasion if used at the wrong time.

Hygiene and washdown

  • Check and clean vehicles, machinery, clothing and other gear that may carry seeds, which can attach to vehicles and clothing.
  • Avoid moving contaminated hay or grain, as seeds can be spread in agricultural produce.
  • 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): Key threatening process. Listed under the EPBC Act, with a national threat abatement plan for invasion by five invasive grass species.
  • 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: Not a priority weed. Not a state or regional priority weed in NSW. 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: Not declared. Not declared under the Landscape South Australia Act 2019. Other laws may still apply.
  • Western Australia: Declared pest (C1), prohibited. C1 Exclusion: to be kept out of WA, or out of the parts of WA where it is not established. Report any sighting to DPIRD. It must not be brought into WA (prohibited organism).
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Declared weed, Class B. Class B: growth and spread must be controlled. All declared weeds are also Class C, so they must not be brought into the NT.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

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)
  • Northern Territory: Territory Parks and Wildlife Conservation Act 1976 (NT), administered by NT Department of Lands, Planning and Environment

Sources