Mexican Feather Grass

​(Nassella tenuissima)

Image: Mexican feather grass, © Molongalo Catchment Group.

What is Mexican feather grass?

  • Mexican feather grass is a potentially serious weed of pastures, native grasslands and woodlands.
  • Mexican feather grass is a declared weed in Tasmania under the Tasmanian Weed Management Act 1999. The importation, sale and distribution of Mexican feather grass are prohibited in Tasmania.
  • Closely related to serrated tussock, and Chilean needle grass, both Weeds of National Significance(WoNS).

Image: Mexican feather grass in a garden situation, © A Maguire.

How to identify Mexican feather grass

Mexican feather grass leaves are 0.25–0.5 mm wide, up to 60 cm long and tightly rolled with overlapped edges. Leaves roll smoothly between the fingers like a needle, but feel coarse when sliding fingers downwards along the leaf blade. The ligule (a small, thin structure at the base of the leaf blade) is 0.5–2.5 mm long, opaque, papery and smooth.

Flowering stems are up to 70 cm high, round, smooth and hairless, with 2–3 unthickened nodes.

The flower head of Mexican feather grass is 15–25 cm long and green or purplish in colour. An identifying feature of the plant is that the flower head does not detach from the plant and it has a leaf-like sheath that encloses its lower section.

Mexican feather grass seeds are 2–3 mm long and encased by two purple or reddish-brown glumes, 6–10 mm long. Another distinguishing feature is the awn, which is 4.5–9 cm long and attached centrally to the end of the seed.

Mexican feather grass is unpalatable to stock, difficult to control and capable of growing in a variety of climates and soil types. It is able to tolerate prolonged periods of drought and can flourish in areas that are heavily grazed.

Mexican feather grass in Tasmania

Mexican feather grass has been recorded in Tasmania several times as an ornamental or garden plant. Mexican feather grass has also been inadvertently imported to some Australian mainland states for propagation for landscaping purposes. 

Mexican feather grass is not naturalised in Tasmania at present. 


Mexican Feather Grass Seed Image: Mexican feather grass, © Molongalo Catchment Group.

What is the legal status of Mexican feather grass in your area?

  • The legal responsibilities of landholders and other stakeholders in dealing with Mexican feather grass are laid out in the Mexican feather grass Statutory Weed Management Plan.  
  • Use Table 1 (Zone A municipalities) to find out whether this weed occurs in your municipality

What you need to do?

If you locate Mexican feather grass anywhere in Tasmania, or if you find a plant that you think could be Mexican feather grass, immediately contact Biosecurity Tasmania on 03 6165 3777 to report this weed. 

See Also

Other useful links
Pest Genie

Nassella species identification comparison table

  Lobed Needle Grass Cane Needle Grass Texas Needle Grass Chilean Needle Grass Serrated Tussock
StatusIntroduced, Declared, an Alert List WeedIntroduced, Declared, an Alert List WeedIntroduced, Declared, an Alert List WeedIntroduced, Declared, Weed of National SignificanceIntroduced, Declared, Weed of National Significance


(outer casing of seed, the 'glume', removed to reveal detail.) (Click to enlarge image*)


'Corona', the collar at seed basePresentPresentPresentPresentAbsent
'Awn', the bristle-like seed tail


double bent

firmly fixed to seed coat


Twisted and bent

35-60mm long

Bent twice with 10-20mm to first bend


Straight or double bent

Firmly fixed seed coat



Readily detached from seed coat

'Cleistogenes', or stem seedsAbsentPresentPresentPresent Absent
'Ligule', the flap at leaf base
(Click to enlarge image*.)

Overall dimensions

0.5-1.0m high and

0.3 -0.5m across

to 1m high,

to 0.3m across

1-1.5m high,

0.2 -0.5m across

1-1.5m high,

0.3 -0.6m across

to 1m high,

to 0.6m acros

​* Images in table:
© 2003 Weed Management Guides, Lobed needle grass, Chilean needle grassSerrated tussock, C'wlth Dept of the Env't & Heritage.
© Chilean Needle Grass & Serrated Tussock Ligule photos: Harry Rose (Wikimedia).


Important Disclaimer
To the extent permitted by law, the Tasmanian Department of Primary Industries, Parks, Water and Environment (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using information or material (in part or in whole) contained on this website.