Nassella trichotoma (Nees) Hack. ex Arechav.
nassella tussock
Caespitose perennial with shoots swollen and white at base, and open ± purple panicle, branching intravaginal. Leaf-sheath to 5 cm, scabrid near ligule and on upper margins, becoming glabrous below. Ligule to 1.5 mm, decurrent, symmetrical or asymmetrical, rounded or apiculate, short-hairy or scabrid. Leaf-blade to 35 cm × 0.5 mm diam., inrolled appearing terete, very stiff, acicular, abaxially markedly antrorsely scabrid, adaxially clothed in short dense hairs; margins smooth. Culm to 70 cm, glabrous except for hairs above and below nodes. Panicle to 25 cm, open, much-branched, drooping, at maturity readily detaching with culm and blowing freely; rachis, branches and pedicels scabrid. Glumes ± equal, 5-8 mm, deeply purple-suffused, 3-nerved, produced into awn c. 2 mm, nerves and margins stiff hairy. Lemma to 2.5 mm, 5-nerved, gibbous, tubercular-scabrid except on margin, lobes short, apiculate; coma present; awn tardily caducous to 35 mm, weakly 1-geniculate, short stiff hairy, column loosely twisted, to 15 mm, arista to 20 mm. Palea c. 1 mm, completely enclosed by lemma, glabrous, hyaline, weakly bifid at apex. Callus to 0.3 mm, blunt, hairs to 1.5 mm. Lodicules 2, to 1 mm in chasmogamous flowers, to 0.6 mm in cleistogamous flowers. Anthers penicillate, in chasmogamous flowers to 2 mm; in cleistogamous flowers 1 fertile anther to 0.7 mm, and 2 aborted anthers to 0.3 mm. Plate 3D.
N.: scattered small infestations from Kaitaia to Coromandel Peninsula, and on east coast to Hastings; S.: east coast from Marlborough to Central Otago. Grasslands and scrub to 300 m.
Naturalised from South America.
An important pastoral weed especially in Marlborough and North Canterbury [Healy, A. J. in Knox, G. A. (Ed.) Nat. Hist. Canty 261-333 (1969)]; the Nassella Tussock Act, 1946, was passed to assist with its control; that was superseded by The Noxious Plants Act, 1978, which embodied most of the original provisions, but the Biosecurity Act 1993 repealed it.
Two species of Austrostipa are at times confused with 0. The abundant A. nodosa is distinguishable by: absence of swollen white bases of shoots, with leaf-sheaths bearing long hairs on margins and terminating in a conspicuous tuft of abundant white hairs up to 1.5 mm long. The pinkness of the inflor-escences and their shimmer in the distance may also mislead, but the heads do not freely detach. Austrostipa scabra lacks the conspicuously swollen bases of nassella tussock, its leaf-blade bears short stiff hairs, and the inflorescence does not readily detach. Differences in lemma shape and size easily separate the two genera.
