Mexican feather grass (Nassella tenuissima)

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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 take over up to 65% of 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

Flowers are:

• green or purplish
• produced on a round, smooth and hairless spike
• on stems up to 80 cm long
• 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 is closely related to serrated tussock (Nassella trichotoma) and Chilean needle grass (Nassella neesiana). The plant height and seeds can help distinguish between these weeds. 

Serrated tussock is shorter (45 cm) and has:

• a fatter seed
• a much smaller awn (25 mm)
• an off-centred awn.

Chilean needle grass is taller (1 m) and has:

• a much larger seed
• a crown of little ‘teeth’ at the base of it’s awn. 

Where is it found?

In New South Wales, Mexican feather grass has been found in gardens at Tamworth, Tenterfield and near Lithgow. The Tamworth plants were found in 2006 and all plants were removed and destroyed. 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.

In 2019 Mexican feather grass was found in gardens around Lithgow. 

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.

How does it spread?

Mexican feather grass reproduces by seed. From mid spring to summer it germinates on well-drained soils where there is little competition from other vegetation. Seeds can be dispersed by becoming attached to clothing, livestock and vehicles, or from 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.

Acknowledgements

Written by Alan Maguire; prepared by Annette M^cCaffery and Annie Johnson; 2013 edition reviewed by Michael Michelmore; edited by Elissa van Oosterhout.

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Control

Physical control

The plant can be dug out and destroyed. Contact your local council for assistance and advice. 

Chemical control

This information applies to all Nassella genus grasses.

Most herbicides used to control Nasella grasses contain either glyphosate or flupropanate. Pasture species have variable tolerance to these herbicides. Check which pasture species are present. Follow up is essential for successful control. 

Herbicides are most effective in combination with healthy, competitive pastures. Long-term herbicide use can lead to weeds developing herbicide resistance.

Always observe grazing withholding periods following herbicide treatments in pastures.

Flupropanate herbicides

Legumes and some native pasture species (e.g. weeping grass, wallaby grass, spear grass) can be killed by flupropanate herbicides. Kangaroo grass and redgrass are more tolerant. 

Flupropanate can remain active in the soil for up to two years. Residual activity depends on the amount of rainfall. Residual activity is longer with low rainfall or drought.  Flupropanate continues killing serrated tussock seedlings until 100mm of leaching rainfall has fallen.

The herbicide washes out faster from sandy soils than clay soils. Do not sow a new pasture or crop until flupropanate is likely to have washed out of the root zone.

Flupropanate takes several months to kill serrated tussock. It may not stop seed production when  applied after mid-August. Apply 2–4 weeks before seed heads emerge (indicated by thickening of tillers). After seeding, use a mix of glyphosate + flupropanate. 

Label rates of flupropanate control serrated tussock with minimal damage to young native trees.

Glyphosate herbicides

Use glyphosate for a complete knockdown of serrated tussock and other weeds. Glyphosate has no residual effect.

Apply glyphosate:

• in spring before crop or pasture in autumn 
• just before sowing in autumn 
• to spot spray mature serrated tussock before seeding.

Avoid using glyphosate when:

• soil is dry
• there are frosts or dew
• dead plant material covers the growing parts of weeds.

Glyphosate can be unreliable when:

• tussock are mature, AND
• growing on fertile clay soils, AND
• there is low rainfall.

Spot spraying

Spot spray individual clumps or small patches year round, before plants set seed. Use a spray shield to minimise damage to surrounding plants. Check paddocks after spraying for any missed plants.

Broadacre spraying

Herbicide can be applied with boomsprays or aircraft for larger areas. There is less chance of damage to non-target plants (particularly trees) using flupropanate.

Weed wipers

Graze to reduce the height of desirable pasture species before using wipers. Both flupropanate and glyphosate are suitable.

Wiping is only effective on large tussocks. Repeat treatment as smaller tussocks mature. Use the wiper in two directions to improve efficacy. 

Herbicide resistance

Herbicide resistant plants spread and are harder to control. Herbicide resistance is more likely to develop when treating large areas with a lot of weeds. To avoid herbicide resistance:

• rotate flupropanate with glyphosate 
• spray before seed set
• use other control methods with herbicide (cropping, pasture, chipping, forestry, grazing and fertiliser)
• reduce populations. 

Check weed survival after spraying. Treat survivors with a different herbicide. 

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
Withholding period: Don't graze cows or goats that are being milked on treated areas. Blanket sprayed pastures - grazing or cutting for stock feed - 120 days. Spot sprayed areas - grazing or cutting for stock feed - 14 days. Don't graze stock on treated areas for 14 days prior to slaughter.
Herbicide group: J, Inhibitors of fat synthesis (Not ACCase 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
Withholding period: Don't graze cows or goats that are being milked on treated areas. Blanket sprayed pastures - grazing or cutting for stock feed - 120 days. Spot sprayed areas - grazing or cutting for stock feed - 14 days. Don't graze stock on treated areas for 14 days prior to slaughter.
Herbicide group: J, Inhibitors of fat synthesis (Not ACCase 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
Withholding period: Don't graze cows or goats that are being milked on treated areas. Blanket sprayed pastures - grazing or cutting for stock feed - 120 days. Spot sprayed areas - grazing or cutting for stock feed - 14 days. Don't graze stock on treated areas for 14 days prior to slaughter.
Herbicide group: J, Inhibitors of fat synthesis (Not ACCase inhibitors)
Resistance risk: Moderate

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PERMIT 9792 Expires 30/11/2025
Glyphosate 360 g/L (Roundup®)
Rate: 3 L per ha
Comments: Broadacre control
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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PERMIT 9792 Expires 30/11/2025
Glyphosate 360 g/L (Roundup®)
Rate: 1 L per 100 L of water
Comments: Spot spray
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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PERMIT 9792 Expires 30/11/2025
Glyphosate 360 g/L (Roundup®)
Rate: 3.3 L per 10 L water
Comments: Wiper suppression
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
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 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 2019