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Serrated tussock - Nassella trichotoma

Weed Seed - Serrated tussock (Nassella trichotoma)

Serrated tussock is difficult to control. It has become one of the most invasive plants in Australia. Mature plants can produce up to 140,000 seeds per year; they can stay viable for many years in the soil. The plant invades grasslands and competes with other species, reducing biodiversity. It is indigestible to livestock, decreasing pasture productivity.

Where it's found

Serrated tussock has not been found in Canada. It is native to South America. It has been introduced to Australia over the last century and has gradually spread over millions of hectares of pasture in the south-eastern part of that country.

What it looks like

Serrated tussock is a perennial grass. Its thin, bright-green, hairless leaves are tightly rolled (they roll smoothly like needles between the index finger and thumb) and have small, easily felt serrations along their edges. Long, purplish, branched seed heads bend toward the ground. Each plant can grow to up to 70 cm tall.

How it spreads

Serrated tussock has branched clusters of flowers (panicles) that break off from the parent plant and are easily carried by the wind for over 20 km. As the panicles move, seeds are dropped. Seeds can also be transported in soil by the muddy wheels of vehicles, in contaminated hay, in seed lots, and on animals and clothing. It is less likely to invade healthy, well-managed grasslands.


Serrated tussock is regulated as a pest in Canada under the Plant Protection Act. It is also listed as a prohibited noxious weed in the Weed Seeds Order, 2016 under the Seeds Act. Importation and domestic movement of regulated plants and their propagative parts is prohibited.

What you can do about it

  • Use clean grain, hay and straw.
  • Use clean, high-quality seed that is certified if possible.
  • Ensure machinery, vehicles and tools are free of soil and plant parts before moving them from one area to another.
  • Contact your local Canadian Food Inspection Agency (CFIA) office if you suspect you have found this invasive plant. The CFIA will follow up and determine if further action is needed.

Learn more about invasive species.

Serrated tussock flower heads
Serrated tussock flower heads
Julia Scher, United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine (Bugwood.org
Serrated tussock flower seed heads
Serrated tussock flower seed heads
Bill Strong, 2008
Tussock of serrated tussock
Tussock of serrated tussock
Bill Strong, 2008