Quick Facts

Quick facts

• Originally from South America, Serrated Tussock (Nassella trichotoma), a Weed of National Significance, is a perennial narrow-leafed, tufted grass to 700 mm tall, highly invasive with serious impacts on the environment, agriculture and the economy.
• Spread only by seed, mature healthy plants can produce up to 100,000-140,000 seeds per year, readily invading pastures, native grasslands and open areas, excluding desirable species. 
• Poses a threat in cool to warm temperate, to sub-tropical and even tropical areas, preferring temperate areas with rainfall from 450-1000 mm, growing in rich to poor degraded soils.
• Serrated Tussock has little nutritional value and severely reduces the carrying capacity of land, and if animals are fed only on Serrated Tussock, the leaves can form balls in the rumen causing loss of condition and eventual death.
• Control is difficult, and herbicide treatment alone usually results in re-infestation of Serrated Tussock from seed in the soil, so it is important to incorporate other control methods in an integrated management strategy.
• All control programs should aim to reduce the amount of seed produced, with prevention the most cost-effective form of weed control, with quarantine early detection and good hygiene within infestations preventing spread.
• Exclusion of Serrated Tussock relies on establishment and maintenance of a competitive pasture that out-competes tussock seedlings and resists re-infestation.

What Does It Look Like?

What is it?

Serrated Tussock (Nassella trichotoma) is an invasive perennial tussock-forming grass that can live for 20 years or more. It has an extensive, wiry and fibrous root system mostly in the top 200 mm of soil although some roots may occur deeper making Serrated Tussock very difficult to pull from the ground. In fertile soil it grows to a height of 600-700 mm, with a diameter at the base to 250 mm. With the dropping seed heads, the plant can have an overall diameter of about 700 mm. Plants growing in infertile conditions are smaller and plants may only attain heights of 150-200 mm. The leaves are narrow (about 0.5 mm in diameter) and tightly rolled, without hairs but with small easily felt serrations along their length (Parsons & Cuthbertson 2001; CRC 2003). Leaves have a opaque-whitish  papery ligule (a small structure arising at at the base of the inner junction of the leaf and stem, wrapping around the stem), 0.25-0.5 mm long occasional to 2.5 mm with a obtuse (blunt or wide point) or truncate (blunt or straight) apex (end).

The Inflorescence (flower heads called panicles) are slender, open branching, and grow to about 250 mm long. Flower heads are normally produced half way up to the top of the plant and are shortly exerted (with a potion of the flower heads extending beyond leaves). The flowering heads contain many whorls of 2-3 branches, each with a single flower at the end, or another branching stem with flowers at the end. Each flowering stem can produce 30 – 200 or more flowers. Each year plants can produce over 100,000 flowers developing in to seeds. Flowers are often with a purplish tinge during flowering. The seeds are always surrounded by papery thin scales (called glumes) 6-10 mm long, normally light to dark purple, tapering to a point. Seeds have a relatively long (15-35 mm) awn, (a hair / bristle like structure) attached off-centred to the back seed, is exerted beyond the glumes. 

The seeds of Serrated Tussock are unique and cannot be confused with any other tussock grasses species (weed or native) in Australia. Serrated Tussock grass seed is only 1.5-2 mm long and 7-10 mm wide with small warts covering the surface. The callus of the seed (the front or pointy end) is bearded (has many tufts of short hairs) that are silky white, extending a quarter to halfway along the seed. The thin awn (a hair / bristle like structure), is attached off-centre at the blunt end of the seed, awn is 15-35 mm long, has several minor bends, but the awn is mostly straight. The awn twists like rope, thinning to a point. No corona is present where the awn attaches to the seed. At maturity the seed heads break off whole (Richardson et al. 2006). When the seed heads are fully developed seeds are golden brown. With age the flowering heads usually droop over and trail along the ground (Campbell & Vere 1995).

Recognition: This species can normally be recognised by the combination of the following characters; small wide seed to 1.5 -2 mm long; awn with off-centre attachment to the seed, thin awn to 25-35 mm long; tussock forming plant with rough leaves; papery ligule, many flowering heads produced mostly within the leaves of plant.  

For further information and assistance with identification of Serrated Tussock contact the herbarium in your state or territory.

Flower colour

Purple-green.

Growth form (weed type/habit)

Grass

Where it currently grows? Preferred habitat

Serrated Tussock is adapted to a wide range of climates and soil types and is spreading from agricultural areas into metropolitan areas with the area increasing since control techniques have failed to contain its spread.

Serrated Tussock is a very invasive weed that is widespread in southeastern Australia (far northeastern New South Wales south to Victoria and eastern Tasmania), covering more than 1.1 million ha. It is capable of withstanding a range of climates but prefers cool temperate areas with an annual rainfall ranging from 450 – 1000 mm.  

Areas affected by Serrated Tussock include, pastures, native grasslands, open scrub and woodland. It will grow on all types of terrain and aspects, from steep, rocky and timbered areas, on low-fertility and dry soils, to fertile moist flats.  It quickly colonises bare ground and disturbed areas such as roadsides, overgrazed pastures or cultivated situations. It will grow in acid soils, but its distribution is limited by salinity and / or water-logging and areas with high summer temperatures (Jacobs & Everett 1993; CRC 2003).

Are there similar species?

Serrated Tussock can normally be recognised when fertile seed is present by the combination of the following characters; small wide seed to 1.5-2 mm long without corona (crown separating the seed and awn); awn with off-centre attachment to the seed; thin awn to 25-35 mm long; tussock forming plant with many flowering heads produced mostly within the plant.  

Serrated Tussock is similar in general appearance and difficult to distinguish morphologically, when not fertile, from other Nassella species as well as several other native tufted grasses with similar narrow, rolled leaves, such as some species of Austrostipa (previously known as Stipa) or Poa.

The fine very rough leaves are characteristic of Serrated Tussock, along with a distinctive ligule. A ligule is a small flap located at the junction of the leaf blade and the leaf sheath, located by tracing a leaf down to where it joins the sheath and bending the leaf back at this point. Serrated Tussock has a white, hairless, membranous to papery ligule 0.25-0.5 mm long (or sometimes to 2.5 mm long), whereas most other grasses it can be confused with have ligules with different colours or hairs, or have no visible ligule. Austrostipa scabra (both subspecies falcata and subspecies scabra) has similar ligules but the leaves, while variably hairy, are not distinctly rough (CRC 2003; Everett et al. 2009).

Why Is It A Weed?

What are its impacts?

Serrated Tussock is a Weed of National Significance as it is regarded as one of the worst weeds in Australia because of its invasiveness, potential for spread, and economic and environmental impacts. In New South Wales alone it has been estimated that the weed has cost more than $40 million in lost production (CRC 2003).

Agriculture: It causes significant problems in grazing lands with poor soil fertility and low rainfall where the benefits of control are marginal. It is also unpalatable to livestock and will only be eaten by sheep and cattle if nothing else is available (Osmond et al. 2008, Parsons & Cuthbertson 2001). Serrated Tussock has no grazing value because of its high fibre and low protein content. Its low nutritional value is insufficient to meet livestock requirements and if live stock are forced to graze pastures containing only Serrated Tussock, the leaves can form indigestible balls in the rumen, causing loss of condition and eventual death (Osmond et al. 2008). Infestations result in a significant loss in livestock production and and Serrated Tussock probably accounts for a greater reduction in pasture carrying capacity than any other weed in Australia (Parsons & Cuthbertson 2001). Dense infestations may completely dominate pastures, making large areas incapable of supporting livestock. Pastures that can normally carry carry 7-15 dry sheep equivalent (DSE) per hectare (ha) can be reduced to a carrying capacity of only 0.5 DSE per ha. In addition, the seeds with awn can contaminate wool (CRC 2003). Its seeds also contaminate hay and grain and other produce (DPI NSW 2019).

Native ecosystems: Serrated Tussock can readily establish in environmentally significant native grasslands reducing biodiversity as dense infestations can out-compete and eliminate most other plants over large areas, also negatively impacting on native fauna (Osmond et al. 2008; Parsons & Cuthbertson 2001).  It can also invade other environmental significant area such as grassy woodlands, scelerophyll forest, dry open woodlands, and coastal vegetation (Osmond et al. 2008)

Urban areas: Serrated Tussock can dominate road sides, parks, neglected areas, railways, power-line easements, reserves, and sporting grounds in and around towns and cities (Osmond et al. 2008). In urban areas it creates a fire hazard (CRC 2003), as the build-up of bio-mass increases fire intensity. Seed heads can catch fire, blow away, and start fires some distance away. Seed heads can also block eves causing increased fire risk. Fire season is increased in areas with large infestations.

How does it spread?

Serrated Tussock disperses and grows from seed, and not by vegetative structures such as rhizomes or perennial roots. Mature plants can produce more than 100,000-140,000 seeds per year. Seeds are the of Serrated Tussock are mainly spread by wind, but is also spread by humans and animals.

Serrated Tussock are well adapted to wind dispersal and once the seed matures it remains on the flowering head that breaks away at the base of the tussock and blows along the ground with surface winds, or is sometimes carried away via above ground thermals. Most seed heads  will not be carried far, but some seed heads can be blown up to 20 km away (Osmond 2008).

Serrated Tussock can also become attached to vehicles and machinery, for example, cultivation implements, vehicle tyres, slashing equipment, tractors, spray units, mowers and slashers, and bottom of vehicles, making it possible to spread Serrated Tussock over large distances.  It may also be transported by moving soil. Seed transported or buried in soil by cultivation can remain dormant for several years and produce seedlings after subsequent soil disturbance.

It can also catch on the fleece of sheep or be picked up in mud on the hooves of livestock. Seed survives the passage through animals, and can survive 10 days in the stomach of ruminant animals that can spread the seed if transported. In Tasmania, quarantine measures are in force to prevent further spread (CRC 2003).

Serrated Tussock seedlings are usually out-competed by other plants, but become competitive under conditions of drought or overstocking when more favourable pasture species are consumed by stock, leaving behind the less palatable Serrated Tussock (CRC 2003).

What is its history in Australia?

Serrated Tussock is thought to have been accidentally introduced into Australia around 1900 (Parsons & Cuthbertson 2001; Michelmore 2003), and was subsequently cultivated as an ornamental tussock grass (Randall pers. comm. in Groves et al. 2005). It was also regarded at one time as a potential pasture species: seed of it was listed in Herbage Abstracts in 1945 as available for exchange with pasture agronomists (Rosengurtt 1945, quoted in Cook & Dias 2006). Serrated Tussock was first noticed to be a problem at Yass in New South Wales in 1935, but it was recognised as a difficult problem in many areas by World War II (CRC 2003). It was first recorded in Victoria in 1954 and Tasmania in 1956 (Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

Preventing the invasion is the cheapest and most effective way of controlling Serrated Tussock.

Chemical control: Serrated Tussock can be killed by several widely used chemicals (Osmond et al. 2008). However, Serrated Tussock is known to have herbicide resistance in some locations in Australia. Herbicide resistance is the ability of a plant to survive and reproduce following application of a herbicide. In addition, herbicide treatment alone that kills target plants will not give long-term control. Spot spraying with a registered herbicide is only effective to control light and scattered infestations with follow-up required.

Non-chemical control: Physical control: Only very young plant can be removed by hand-pulling. The extensive root system on mature to adult plants prevents hand-pulling . However, Chipping mature plants out the ground with a mattock before tussocks set seed can kill most plants. However, for large plants where moist soil is present around the remaining roots in the ground, follow-up treatment is required as plant can re-grow from these roots.

Competition and management: On arable land, Serrated Tussock can be successfully controlled with a program of ploughing, cropping and pasture improvement. Invasion from wind-blown seeds can be reduced by planting windbreaks. Sowing perennial pastures such as Phalaris and improved pastures in general should be established to compete with Serrated Tussock and prevent re-invasion. Stock grazed on Serrated Tussock producing mature seed should be placed in a holding paddock for 10 days before moving them into a clean paddock (CRC 2003) as seeds can remain viable in the stomach of animals for up to 10 days.

Mulching, the application of material over the ground such as straw, wood chips, carpet or plastic sheeting will prevent the growth of all plants, including Serrated Tussock and beneficial plants. Suitable for small infestation in native or urban areas, and large infections in agricultural situations.

Fire can be used to reduce bio-mass and kill seeds on the plant and soil surface, but will not kill adult plants or buried seed. Fire stimulates re-growth and mass germination of seed so vigorous and planned follow-up is required to control plants.

Biological control: Although Serrated Tussock has also been recognised as a target for biological control through a cross-jurisdictional government process, there are currently no effective useful biological control agents. Three biological control agents against Serrated Tussock have been investigated for release into Australia: a rust, Puccinia nassellae, a smut, Ustilago spp., and another fungus. A fungus that occurs naturally on native Austrostipa spp. has also been observed to attack Serrated Tussock in the field (CRC 2003), but none of the three agents proved to be a successful candidate for further testing as biological Control agents.

For further information and detailed methodology of control is outlined in (Osmond et al. 2008) and in various publication on the 'Victorian Serrated Tussock Working Party' (2020) web page (http://www.serratedtussock.com/management/fact-sheets)

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Serrated Tussock is a perennial grass that reproduces from seed. It builds large seed banks in the soil and, although most seed die within three years, some may stay viable for decades.

Seeds germinate at any time of year but mostly in autumn and winter. Seedlings grow slowly and need to establish before summer as competition for moisture and light can lead to stress and death.  Plants rarely flower in the first year of growth; flowers and seeds are usually produced in the second summer. Flower stalks usually appear in spring, but in dry years the plants flower earlier. By the time it flowers, Serrated Tussock leaves are long and drooping. The seed ripen with 10 weeks of flowers being produced and seeds remain attached to the stem that breaks-off at the base and is blown away aiding dispersal. The plant mainly grows during spring and early summer, and is bleached by frosts to golden yellow tussocks in autumn and winter (CRC 2003).

Where Is It Found?

Which states and territories is it found?

ACT, NSW, SA, TAS, VIC.

What areas within states and territories is it found?

 In New South Wales it is widespread on the tablelands where it causes serious impacts on pastures and native habitats, but it also grows on the coast and is moving farther west of the tablelands. In Victoria the area covered has increased four-fold over the past 20 years. In Tasmania the weed is a problem in the southeastern part of the state, with smaller infestations on King Island in Bass Strait (CRC 2003).

In South Australia a single population was found in 2002 in a suburban garden, which may have since been eradicated (Jessop et al. 2006) and more recently several plants have been found in the south-east of SA.

Not yet found in Queensland, Northern Territory or Western Australia.

Where does it originate?

There are about 80 species of Nassella in the Americas, with none of the species occurring in Australia native (Everett et al.). Serrated Tussock is native to South America (Argentina, Bolivia, Brazil, Chile, Paraguay, Peru and Uruguay).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

YES

Where is it a declared weed?

Declared in all States and Territories.

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Nassella trichotoma

Other scientific names (synonyms)?

Stipa trichotoma Nees

Does it have other known common name(s)?

 Yass River Tussock, Yass Tussock, Nassella Tussock (NZ).