Trisetum tenellum (Petrie) A.W.Hill
≡T. antarcticum subsp. tenellum Petrie, T.N.Z.I. 44: 187 (1912), "tenella"
≡T. antarcticum var. tenellum (Petrie) Cheeseman Man. N.Z. Fl. 169 (1925);
Lectotype: WELT 68724! D. P[etrie] Hooker River, Mt Cook, 13.2.1911 (designated by Edgar 1998 op. cit. p. 558).
Small tufts 2-35-(55) cm, with slender, often almost filiform culms usually » grey-green often involute leaves at maturity; branching extravaginal. Leaf-sheath 0.5-2 cm, glabrous, or sparsely finely prickle-toothed on ribs to densely pubescent. Ligule 0.2-1 mm, truncate or rounded, ciliate. Leaf-blade 1-12-(18) cm × 0.3-1.5-(2) mm, abaxially glabrous to finely scabrid to pubescent, sometimes with scattered long hairs, adaxially ribbed, minutely scabrid to shortly pubescent; margins minutely prickle-toothed, occasionally with scattered long hairs. Culm (1)-2-20-(45) cm, internodes glabrous, or sometimes densely pubescent with ascending or tangled spreading hairs, occasionally hairs retrorse below. Panicle 0.5-8.5 × 0.5-1.2 cm, ± spike-like with very short close-set branches but rachis visible, or more open with short ascending branches; rachis glabrous and branches with a few minute prickle-teeth, or rachis and branches pubescent. Spikelets (3.5)-4-5.5 mm, pale green or red-tinged. Glumes subequal, membranous, keels with prickle-teeth in upper ⅓ to upper ½; lower ≤ upper, elliptic, very rarely oblong-lanceolate, upper ≤ spikelet, broadly elliptic; margins with very minute prickle-teeth near obtuse to acute rarely almost mucronate tip. Lemma 3.5-5 mm, minutely bidentate, papillose, minutely scabrid near keel; awn 2-3-(4) mm, insertion in upper ¼ of lemma. Palea minutely prickle-toothed on keels except near base and sparsely minutely prickle-toothed on margins. Callus hairs 0.2 mm. Rachilla hairs few, to 0.8 mm. Lodicules c. 0.7 mm, glabrous. Anthers 0.6-1.3 mm. Gynoecium: ovary c. 0.7 mm; stigma-styles c. 1.2 mm. Caryopsis c. 2 × 0.5 mm.
S.: north-west Nelson and to east of Main Divide in Marlborough and from south of Arthur's Pass and Banks Peninsula, extending slightly to the west in Fiordland. Rocky or stony ground on moraines, scree, river beds, and eroded sites, on limestone, marble, and ultramafic sites in tussock grassland, fellfield and herbfield, sometimes in swampy sites; (300)-600-1860 m. FL Dec-Feb.
Endemic.
Plants with pubescent culms, panicle-rachis and branches are commonly found in north-west Nelson, and occasionally elsewhere throughout the range of the species, sometimes growing with plants with glabrous culms.
Trisetum tenellum occupies ultramafic sites in Nelson, Marlborough, and Southland, but plants there are indistinguishable from those elsewhere.
Laing, R. M. and Gourlay, H. W. T.R.S.N.Z. 64: 3 (1934) listed "Trisetum tenellum (Petrie) Allan and Zotov (Sp. ined.)" in anticipation of a taxonomic revision by Allan and Zotov which was never written. Laing and Gourlay therefore made no new combination but A. W. Hill who cited the basionym validly published the new combination as T. tenellum.
