Mexican feather grass (Nassella tenuissima)

Mexican feather grass grows in dense clumps. It invades pastures and bushland.

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How does this weed affect you?

Mexican feather grass:

• takes over pastures 
• is unpalatable to stock and reduces pasture quality
• contaminates hay and grain
• invades native grasslands and woodlands.

It is hard to get rid of and has the potential to grow on 65% of land in NSW.

What does it look like?

Mexican feather grass grows in upright tussocks up to 70 cm tall. The leaves in the centre of the clump are usually the tallest and upright but may droop over at the top. Leaves at the edge of the clump are often shorter and bend away from the plant.

Leaves are: 

• 0.25–0.5 mm wide
• up to 60 cm long
• tightly rolled 
• overlapped at their edges
• smooth if you roll them between your fingers
• coarse if you slide your fingers down the leaf. 

Mexican feather grass has a small, thin structure at the base of the leaf blade. This is a ligule, and can look like a small piece of tissue paper. The ligule is:

• 0.5–2.5 mm long 
• papery and smooth
• milky coloured

Seedheads are:

• green or purplish
• produced on a round, smooth and hairless spike
• on stems up to 70 cm long (occassionally longer but these longer stems bend over)
• clustered in a group 15–25 cm long at the end of the spike
• with a sheath that looks like a leaf at the bottom of the flowers
• hard to pull off the plant.  

Seeds are:

• 2–3 mm long
• held inside two purple or reddish-brown structures, 6–10 mm long called glumes
• with an awn (looks like a bristle or thick hair) at the end of the seed
• the awn is 4.5–9 cm long and attached at the centre of  the seed end.

Similar looking plants

Mexican feather grass looks similar to Serrated tussock (Nassella trichotoma) which has drooping flower heads, rather than erect flower heads. Serrated tussock is also shorter (45 cm), has a wider seed, and a much smaller (25 mm) awn. 

Where is it found?

Mexican feather grass has been found in gardens:

• in Tenterfield (Northern Tablelands) in 2006
• in Tamworth (North West) in 2006
• around Leeton (Riverina) in 2018
• around Lithgow (Central Tablelands) in 2019
• in Barden Ridge (Greater Sydney region) in 2020.  

All of these plants have been controlled or under an eradication program.

In 2008 a retailer sold potted plants of Mexican feather grass that were labeled with another name. All plants in NSW were quickly recovered and destroyed. However, some plants in ACT and Victoria had been sold on and planted into gardens.

Mexican feather grass is native to southern USA, Central and South America.

What type of environment does it grow in?

Mexican feather grass:

• survives in many climates and soil types
• competes strongly with pastures, grasslands and woodlands
• tolerates long drought
• flourishes in heavily grazed areas.

Maps and records

• Recorded presence of Mexican feather grass during property inspections (Map: Biosecurity Information System - Weeds, 2017-2024)
  These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.
  
  

How does it spread?

By seed

Each Mexican feather grass plant can produce up to 100 000 seeds per year.  Most seeds germnate within two years but they can live in the soil for at least 7 years before germinating. From mid spring to summer seeds germinate on well-drained soils where there is little competition from other vegetation. 

Seeds are spread by:

• the wind
• attaching to clothing, livestock and vehicles
• movement of contaminated seed and fodder.

Mexican feather grass was accidentally introduced as a garden plant. It’s been sold through nurseries under the following incorrect names:

• elegant spear grass (Austrostipa elegantissima)
• Stipa lessingiana
• Stipa capillata
• Stipa capriccio
• Stipa Regal Sensation. 

Online overseas seed companies have marketed the plant under various names including:

• Stipa tenuissima
• Stipa tenaccissima
• elegant spear grass
• white tussock
• Texas tussock grass
• ponytail grass.

References

Csurhes, S. (2008). Mexican feather grass (Nassella tenuissima)—Pest plant risk assessment, Queensland Department of Primary Industries and Fisheries, Brisbane

Humphries, T., & Florentine, S. K. (2021). A Comparative Review of Six Invasive Nassella Species in Australia with Implications for Their Management. Plants, 10(6), 1036.

Maguire, A. (2005.) Mexican feather grass. NSW DPI Agfact P7.6.60

Moran, N. P., Rowles, A. D., & Constantine, A. B. (2018). 10 years after Victoria’s major Mexican feather grass incursion: Assessing eradication methods and germination behaviour. In Weed Biosecurity—Protecting Our Future, Proceedings of the 21st Australasian Weeds Conference, Sydney, Australia, 9–13 September 2018 (pp. 109-114). Sydney, Australia: Council of Australasian Weed Societies Inc..

Victorian Department of Primary Industries (2004). Landcare Notes – Mexican feather grass: State prohibited weed, Frankston.

More information

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Control

 

Herbicide options

See Using herbicides for more information.

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PERMIT 9792 Expires 30/11/2025
Flupropanate 745 g/L (Tussock®)
Rate: 1.5 to 3 L per ha
Comments: Broadacre control. Best results are achieved when applied to actively growing stress free weeds, particularly in warm periods. See permit for critical comments.
Withholding period: Spot spray: Do NOT graze or cut for stock feed for at least 14 days. Blanket spray: Do NOT graze, or cut for stock feed for at least 4 months. If stock are grazed in treated areas after required time has passed, remove stock from treated areas and do NOT slaughter or milk for human consumption until they have been on clean feed for at least 14 days.
Herbicide group: 15 (previously group J), Inhibition of very long chain fatty acid synthesis (VLCFA inhibitors)
Resistance risk: Moderate

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PERMIT 9792 Expires 30/11/2025
Flupropanate 745 g/L (Tussock®)
Rate: 100 to 300 mL per 100 L of water
Comments: Spot spray control. Best results are achieved when applied to actively growing stress free weeds, particularly in warm periods. See permit for critical comments.
Withholding period: Spot spray: Do NOT graze or cut for stock feed for at least 14 days. Blanket spray: Do NOT graze, or cut for stock feed for at least 4 months. If stock are grazed in treated areas after required time has passed, remove stock from treated areas and do NOT slaughter or milk for human consumption until they have been on clean feed for at least 14 days.
Herbicide group: 15 (previously group J), Inhibition of very long chain fatty acid synthesis (VLCFA inhibitors)
Resistance risk: Moderate

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PERMIT 9792 Expires 30/11/2025
Flupropanate 745 g/L (Tussock®)
Rate: 500 mL per 10 L water
Comments: Wiper suppression. Ensure weeds are at least 15 cm above species to be retained. Apply when weeds are actively growing. See permit for critical use comments.
Withholding period: Spot spray: Do NOT graze or cut for stock feed for at least 14 days. Blanket spray: Do NOT graze, or cut for stock feed for at least 4 months. If stock are grazed in treated areas after required time has passed, remove stock from treated areas and do NOT slaughter or milk for human consumption until they have been on clean feed for at least 14 days.
Herbicide group: 15 (previously group J), Inhibition of very long chain fatty acid synthesis (VLCFA inhibitors)
Resistance risk: Moderate

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PERMIT 9792 Expires 30/11/2025
Glyphosate 360 g/L (Various products)
Rate: 3 L per ha
Comments: Broadacre control. Apply to actively growing, stress free plants. Best control occurs when weeds are at the early seed head stage. See permit for critical use comments.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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PERMIT 9792 Expires 30/11/2025
Glyphosate 360 g/L (Various products)
Rate: 1 L per 100 L of water
Comments: Spot spray actively growing, stress free plants. Best control occurs when weeds are at the early seed head stage. See permit for critical use comments.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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PERMIT 9792 Expires 30/11/2025
Glyphosate 360 g/L (Various products)
Rate: 3.3 L per 10 L water
Comments: Wiper suppression. Ensure weeds are at least 15 cm above species to be retained. Apply when weeds are actively growing. See permit for critical use comments.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area	Duty
All of NSW	General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
All of NSW	Prohibited Matter A person who deals with prohibited matter or a carrier of prohibited matter is guilty of an offence. A person who becomes aware of or suspects the presence of prohibited matter must immediately notify the Department of Primary Industries

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Reviewed 2021