Nassella Tussock (Nassella trichotoma) is a highly invasive, perennial tussock-forming grass from South America and a Weed of National Significance in Australia. It spreads only by seed, with large plants producing up to 100,000–140,000 seeds per year, and can rapidly invade pastures and native grasslands. It has little feed value and can severely reduce carrying capacity; livestock forced to graze it may lose condition and can die. Control is difficult because reinfestation from soil seedbanks is common.
Identify it
Field cues
01Tussock-forming grass with very fine, tightly rolled, thread-like leaves (about 0.5mm diameter)
02Leaf edges feel finely serrated when rubbed from tip toward the base
03White, hairless ligule about 0.5–1mm long at the leaf–sheath junction
04Open, branched flowerhead with a purple tinge as seeds ripen; seedheads droop and can break off
05Small seeds (about 1.5–2mm) with a twisted awn about 15–35mm long
Distribution records are indicative. Always confirm current status with your state biosecurity authority.
Found in: pastures, native grasslands, open woodlands, disturbed areas, roadsides, grassy woodlands, dry forests, dry coastal vegetation, urban wasteland.
Management is challenging because plants produce very large numbers of wind-dispersed seeds and can build long-lived soil seedbanks. Herbicide-only programs commonly reinfest from seed, and resistance to some herbicides occurs in some areas. Effective programs focus on preventing spread, reducing seed production, and maintaining strong competition from desirable pasture or groundcover to limit reinvasion.
1
Prevent seed spread on machinery
Clean down slashers and other machinery before moving from infested areas to clean areas to avoid carrying seed.
2
Remove isolated plants before seed set
Hand-pull very young plants or chip out tussocks with a mattock before seed set to reduce seed input to the soil.
3
Maintain competitive groundcover
Establish and maintain a healthy, competitive pasture to suppress seedling establishment and reduce reinvasion.
Registered herbicide options
FlupropanateGroup 15 · 745 g/L
Ground application, apply September to March and June to August inclusive. Source ↗
FlupropanateGroup 15 · 745 g/L
Spot spray, can be applied all year round. Source ↗
FlupropanateGroup 15 · 86.9 g/kg
Granular application, apply February to December inclusive, ideally during the vegetative stage of growth. Source ↗
Boom spray, apply to actively growing, stress-free plants. Source ↗
Use chemicals to the label. Always read the current APVMA-approved label before application.
Check permit conditions for your state, as some uses are limited to council or government staff.
Aquatic situations require products registered for use in or near water.
Why it matters
Impacts
High invasion and reinfestation risk
Plants produce very large numbers of seeds and can build long-lived soil seedbanks; seedheads can be windblown long distances, enabling rapid spread and reinfestation after control.
Fire hazard
Dense infestations can pose a serious fire hazard, with recorded burn intensity up to 7 times greater than native grasslands; seedheads can accumulate against structures and along fence-lines.
Herbicide resistance risk
Resistance to flupropanate has occurred in some areas, and repeated use of the same herbicide can increase resistance risk.
Toxicity note (livestock): Low feed value and poor digestibility can cause severe livestock health impacts when it is the main feed source.
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