Mexican feather grass, is a potentially serious weed of pastures, native grasslands and woodlands. It is a highly adaptable grass that has the potential to infest up to 65% of New South Wales (NSW), causing major economic and environmental damage.
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 is closely related to serrated tussock (Nassella trichotoma), an invasive weed of temperate grasslands, and can only be distinguished when in flower. Mexican feather grass was initially found in some NSW nurseries, mislabelled and marketed as ‘elegant spear grass’, a name given to the native grass Austrostipa elegantissima.
During 2008, a wholesale nursery based in Victoria imported seed of ornamental stipoid grasses. It is believed that the seed was either mislabelled or contaminated with Mexican feather grass seed, which was then propagated, sold and distributed. The plants may have been sold under the names of Stipa lessingiana, S. capillata, S. capriccio or Stipa Regal Sensation.
Online overseas seed companies have also marketed the plant under various names including Stipa tenuissima, Stipa tenaccissima, elegant spear grass, white tussock, Texas tussock grass and ponytail grass.
Mexican feather grass reproduces by seed. From mid spring to summer it germinates freely 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 is a dense, upright tussock up to 70 cm.
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 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.
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.
Written by Alan Maguire; prepared by Annette McCaffery and Annie Johnson; 2013 edition reviewed by Michael Michelmore; edited by Elissa van Oosterhout.
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State Prohibited Weed
The plant must be eradicated from the land and that land must be kept free of the plant