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

dielsii- in honour of Friedrich Ludwig Emil Diels (1874–1945), German botanist.

Published in
Austral. Syst. Bot. 10: 431 (1997).

Common synonyms
Plectrachne dielsii C.E.Hubb.

Habit
Perennial, densely tufted. Culms erect, 60–250 cm tall. Lateral branches simple. Leaf-sheaths without exudate, glabrous on surface. Leaf-sheaths outer margin hairy. Leaf-sheath auricles absent. Ligule a fringe of hairs. Leaf-blades aciculate, conduplicate, 15–50 cm long, 1–2 mm wide, coriaceous, rigid. Leaf-blade surface hairless throughout or except near base. Leaf-blade apex pungent.

Inflorescence
Inflorescence compound, a panicle. Panicle open, 24–30 cm long, 4–7 cm wide. Panicle axis scaberulous. Panicle branches capillary, scaberulous.

Spikelets
Spikelets solitary. Pedicels flexuous, scaberulous. Fertile spikelets many flowered, comprising 3–4 fertile florets, with diminished florets at the apex, elliptic, laterally compressed, 10–15 mm long, breaking up at maturity. Spikelets disarticulating below each fertile floret. Spikelet callus 0.7 mm long, bearded, base obtuse or acute. Floret callus pubescent, acute.

Glumes
Glumes persistent, similar. Lower glume elliptic, 6–14 mm long, 100% length of upper glume, chartaceous or scarious, 3–9-nerved. Lower glume surface asperulous, glabrous. Lower glume apex entire, emarginate or obtuse or acute or acuminate, muticous or mucronate. Upper glume elliptic, 6–14 mm long, 130% of length of adjacent fertile lemma, chartaceous or scarious, 3–9-nerved. Upper glume surface asperulous, glabrous. Upper glume apex entire, emarginate or obtuse or acute or acuminate.

Florets
Fertile lemma oblong, 5–11 mm long, cartilaginous or coriaceous, 3–11-nerved. Lemma surface pubescent. Lemma apex lobed, 3-fid, with lobes 0.8–2.5 mm long, 3-awned. Median (principal) awn 8–10 mm long overall. Lateral lemma awns present, arising on apex of lobes, shorter than principal. Palea 6–9 mm long, 2-nerved. Palea surface glabrous or pilose or hirsute. Apical sterile florets resembling fertile though underdeveloped. Lodicules 2, fleshy. Anthers 3, 3–6 mm long. Grain with adherent pericarp.

Continental Distribution:
Australasia.

Australian Distribution:
Western Australia: Irwin, Avon.

Classification. (GPWG 2001):
Chloridoideae: Triodieae

Notes
Native. On sandplains and near gorges, in white or grey sand over sandstone or with lateritic gravel; flowers July–Sept.