Chilean needle grass negatively impacts farming and the economy by smothering other grass species and reducing pasture capacity as livestock avoid it. Its sharp seeds can injure livestock, leading to downgraded wool, skins, hides and carcasses, with lambs being particularly vulnerable to getting seeds in their eyes and being blinded.

Chilean needle grass spreads rapidly and seeds remain viable for over 12 years, spreading via animals, vehicles and humans. Ensuring vehicle hygiene and farm biosecurity is crucial to prevent its spread, particularly through transporting animals, hides, fleeces, contaminated feed, hay, soil, plant matter, water and moving machinery.

• Size: Chilean needle grass forms dense tufts up to 1 metre tall.

• Leaves: Bright green leaves are harsh to touch.

• Flowers: It produces purple-tinged flowers from late October to March that ripen into hard, sharp seeds with long twisting tails, that help them attach to animals and soil.

• Root system: It has an extensive fibrous root system making it very difficult to pull from the ground.

• Similar Species: Similar tufted grasses include Nassella tussock (Nassella trichotoma), which has narrower, grey-green, wiry leaves, and ripgut brome, with light green, flat, soft leaves. Compared to Nassella tussock, Chilean needle grass grows in denser clumps.

• Habitat: Thrives in various habitats, particularly in high-producing grasslands.

Chilean needle grass is easiest to spot from late October until March during its flowering and seeding stages, appearing as tall tufts of grass compared to shorter grazed plants. Identification is more challenging outside this period.

To prevent the establishment of Chilean needle grass in Otago and its negative environmental and economic effects, it is in the exclusion programme of the Otago Regional Pest Management Plan (2019–2029).

All Nassella species, including Chilean needle grass, are declared an unwanted organism in the National Pest Plant Accord (NPPA). Any species declared a pest under the NPPA cannot be sold or be in a place where plants are being sold. Pest plants cannot be propagated, bred, multiplied, communicated, released, caused to be released, or otherwise spread.

ORC carries out surveillance to detect exclusion pests and help prevent them from becoming established and spreading in Otago. Early detection and a rapid response to invasion are critical to preventing the establishment and spread of these pests in Otago.

Do not attempt to undertake control of Chilean needle grass yourself. Report any sightings to ORC.