serrated tussock

Nassella trichotoma

a tussock-forming, long-lived grass with very fine and highly inrolled leaves (less than 0.5 mm wide).

the margins of these leaves are very finely toothed, hence the common name 'serrated tussock'.

stems and leaves are upright at first (20-70 cm tall), but become drooping or trailing in nature as they age.

the seed-head is an open branched panicle (8-25 cm long) with many flower spikelets that are borne singly.

these flower spikelets are elongated in shape (4-9 mm long) and topped with an awn (15-35 mm long).

the mature 'seed' has an obscure ring of tiny hairs where the bent and twisted awn attaches to the top of the seed.

Common names 
Also known as: nassella tussock, Yass River tussock, Yass tussock,
Flowering time 
Flowering occurs mostly during late spring and summer.
Native to southern South America.
State declaration 
Category 1
Council declaration 
As per State Declaration
Known distribution 

Widely naturalised in south-eastern Australia (i.e. in eastern New South Wales, the ACT, many parts of Victoria and in Tasmania).


A weed of pastures, grasslands, open woodlands and drier forests (particularly in highland areas). Also found along roadsides, in disturbed sites and in waste areas.


A long-lived (i.e. perennial) tussock-forming grass usually growing 20-70 cm tall.

Serrated tussock (Nassella trichotoma) is one of the Weeds of National Significance (WoNS) in Australia, and is regarded as an environmental weed in Victoria, New South Wales, the ACT and  Tasmania.

Stem and leaves 

The flowering stems (i.e. culms) are much branched and drooping at maturity.

Large numbers of thin, wiry leaves (15-50 cm long) are produced by each tussock, mostly near the base of the plant. These leaves (only 0.2-0.6 mm wide) are very thin (i.e. filiform) and very tightly rolled (i.e. convoluted), giving them a cylindrical (i.e. terete) appearance. Leaf sheaths and blades are mostly hairless (i.e. glabrous) with very fine teeth along their margins. Where the leaf sheath meets the leaf blade there is a small membranous structure (i.e. ligule) that is 0.5-2.5 mm long, but is usually less than 1 mm long.

Flowers and fruits 

The seed-head is a branched open panicle usually 8-25 cm long, but occasionally reaches up to 40 cm in length. The inconspicuous flower spikelets are borne singly at the tips of the seed-head branches, and each flower spikelet contains a single tiny flower (i.e. floret) and two bracts (i.e. glumes). These flower spikelets (4-9 mm long) are elongated and cylindrical (i.e. lanceolate and terete) in shape and topped with a long awn. Flowering occurs mostly during late spring and summer.

When mature the 'seed' separates from the bracts (i.e. glumes), which remain on the seed-head branches for some time afterwards. The mature 'seed' has a sharpened, hairy tip (i.e. pilose callus) at one end and a twisted, bent awn (15-35 mm long) at the other end. Where the awn attaches to the seed there is an obscure collar-like ring of tiny hairs (i.e. coma). Hidden within the hard-coated 'seed', which consists of two reddish-brown or purple coloured bracts (i.e. the palea and lemma), is the small (1.2-2 mm long) dark brown-coloured, and oblong -shaped grain.

Reproduction and dispersal 

This species reproduces via seed. These seeds are most commonly spread by wind and also become attached to animals, clothing and vehicles. They may also be dispersed in contaminated agricultural produce (e.g. fodder) and soil.