Common name
Buck Spinifex

Derivation
Triodia R.Br., Prodr. 182 (1810); from the Greek treis (three) and odous (tooth), referring to the 3-toothed or 3-lobed lemmas.

mitchellii- in honour of Thomas Livingston Mitchell (1782–1855). Scots-born Australian surveyor and explorer.

Published in
Fl. Austral. 7: 606 (1878).

Common synonyms
Triodia hostilis Domin
Triodia mitchellii Benth. var. breviloba N.T.Burb.
Triodia mitchellii Benth. var. ubivagina N.T.Burb.

Habit
Perennial, densely tufted. Stolons absent or present. Basal leaf sheaths persistent and investing base of culm, with compacted dead sheaths. Culms 15–200 cm tall. Leaves cauline, distichous. Leaf-sheaths longer than adjacent culm internode, resinous. Ligule a fringe of hairs. Leaf-blade base without a false petiole. Leaf-blades curled or flexuous, flat or conduplicate or involute, 30–60 cm long, 0.7–3.5 mm wide, coriaceous, rigid, resinous. Leaf-blade margins scabrous. Leaf-blade apex attenuate, hardened.

Inflorescence
Inflorescence compound, a panicle. Panicle open or contracted, lanceolate or elliptic or oblong or ovate, dense or loose, 10–26 cm long, 2–4(–8) cm wide. Primary panicle branches appressed or ascending.

Spikelets
Spikelets solitary. Fertile spikelets many flowered, comprising 5–6 fertile florets, with diminished florets at the apex, elliptic, laterally compressed or terete, 4.5–18.5 mm long, breaking up at maturity. Spikelets disarticulating below each fertile floret. Spikelet callus 0.2–0.3 mm long, bearded, base obtuse or acute.

Glumes
Glumes persistent, similar, thinner than fertile lemma. Lower glume elliptic, 4–10 mm long, equalling upper glume, scarious or cartilaginous, 3(–5)-nerved. Lower glume surface smooth or asperulous, rough on nerves, glabrous or pubescent, hairy below. Lower glume inner surface pubescent. Lower glume apex entire or dentate or lobed, 2–3-fid, obtuse or acute or acuminate, muticous. Upper glume elliptic, 4–10 mm long, 120–160% of length of adjacent fertile lemma, scarious or cartilaginous, 3(–5)-nerved. Upper glume surface smooth or asperulous, rough on nerves, glabrous or pubescent, hairy below. Upper glume inner surface pubescent. Upper glume apex entire or dentate or lobed, 2–3-fid, obtuse or acute or acuminate, muticous.

Florets
Fertile lemma oblong, 4–7 mm long, cartilaginous or coriaceous or indurate, 3–13-nerved. Lemma lateral nerves with distinct primaries but obscure intermediates, absent or obscure below. Lemma surface pubescent or hirsute. Lemma apex dentate or lobed, 3-fid, with lobes 0.5–3 mm long, acute, incised 33% of lemma length, muticous. Palea 100% of length of lemma. Palea keels wingless or winged, narrowly winged, ciliolate. Palea surface glabrous or pubescent. Apical sterile florets resembling fertile though underdeveloped. Anthers 3, 2–3 mm long.

Continental Distribution:
Australasia.

Australian Distribution:
Northern Territory, Queensland, New South Wales.

Northern Territory: Darwin & Gulf. Queensland: Burke, North Kennedy, South Kennedy, Port Curtis, Leichhardt, Burnett, Wide Bay, Darling Downs, Gregory North, Mitchell, Warrego, Maranoa. New South Wales: Northern Tablelands, North-Western Slopes, Central-Western Slopes, North-Western Plains.

Classification. (GPWG 2001):
Chloridoideae: Triodieae

Notes
Qld, N.S.W. and one record from NE N.T. Shallow often stony soils on hillslopes, ridges and plateaux of sandstone, quartzite, granite, limestone, slates and laterite, often among boulders or outcrops; also in depressions, on sandy creek banks, hard red soils, and sand dunes and other deep sandy soils; flowers all seasons.
The highly resinous leaves, panicle branches and glumes; long-bearded orifice margins; 3-nerved cartilaginous glumes; loose exserted florets; mostly hairy deeply lobed lemmas; winged palea keels; and large branched rather dense panicle are diagnostic features.
Allied with T. pungens, but differing in foliage and lemma indumentum, spikelet morphology and panicle structure.