T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Nassella trichotoma (Nassella tussock)

Kingdom: Plantae
(unranked): Angiosperms
(unranked): Monocots
(unranked): Commelinids
Order: Poales
Family: Poaceae
Genus: Nassella
Species: N. trichotoma
Binomial name: Nassella trichotoma
Synonyms: Nassella tenuissima, Agrostis trichotoma, Caryochloa trichotoma, Oryzopsis trichotoma, Piptatherum macratherum, Piptochaetium trichotomum, Stipa macrathera, Stipa tenella, Stipa trichotoma, Urachne macrathera, Urachne trichotoma
Common name: Serrated tussock, Serrated tussock grass, Nassella tussock, Finestem needlegrass, Needlegrass

Nassella trichotoma is a type of bunchgrass plant, native to Argentina, Uruguay, Chile, and Peru. It has been present in New Zealand since 1860. Since the 1940s it has been classed as an unwanted organism by Biosecurity New Zealand. In 1946 the Nassella Tussock Act became law – the only Act referring to a single weed species. It a serious weed because of its invasiveness, environmental impacts and its economic effect of reducing the productivity of pastures. Nassella trichotoma is of low nutritional quality making infested lands inadequate for supporting livestock
Sheep if forced to eat tussock, they will lose weight and can die as they cannot properly digest the leaves.
Nassella trichotoma is prevalent in North Canterbury and Marlborough, where it can form dense stands which are difficult to manage.

Nassella trichotoma is a perennial tussock grass which grows up to 70 cm high and 80cm wide and forms dense clumps. The plant base is about 25 cm across. Each stem is swollen just above ground level – like a shallot. 
The leaves which are a light green/yellowish-green are thin and tightly rolled, about 0.5 mm in diameter. The leaf blade has serrations along the margin. The leaf sheaths are white to light brown. The ligule is short (1 – 2 mm), white, hairless. Auricles are absent.
Nassella trichotoma flowers appear during spring and early summer on open, branching inflorescences (25 – 95 cm long). The florets have a long awn about 2.5 cm long. The flowering stems can be up to 1 m tall and they give the tussock a purplish tinge. 
Seeds (grain) are produced from November to January and they are purplish in colour and they have a 3 mm long bristle. A mature plant can produce over 100,000 seeds per year. The lightweight seeds are spread by the wind and can travel as far as 16 km. They are also spread on boots, clothing, wool, animal pelts
It has a deep fibrous root system that can grow 1.7 m below the surface. and can live for over 20 years. 



Flowerheads are open panicles to 25 cm long; they break off at maturity and blow along. Spikelets are 1-flowered and have 2 purplish glumes.

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/