Tall tussock with dark green, persistent, scabrid leaves on brown, hairy sheaths. Sheaths to 20 cm, entire, persistent, becoming fibrous, abundant deciduous hairs to 4 mm long between nerves, on margins and at apex. Ligule to 1 mm. Lamina to 80 cm × 4 mm, flat or folded, many nerved, persistent, abaxially with abundant prickle teeth above, very occasionally with long hairs below, adaxially glabrous; margin with long hairs below soon becoming very scabrid. Culms to 2 m, internodes glabrous or with dense short hairs below nodes. Inflorescence to 35 cm; rachis and pedicels short stiff hairy, but rachis sometimes glabrous in North I. plants. Spikelets of up to 6 distant florets. Glumes hyaline, scabrid, often bifid at apex, < adjacent lemma lobes; lower to 7 mm, 1-nerved, upper to 10 mm, 3-5-nerved. Lemma to 6 mm, scabrid especially above; hairs long at margin and usually aside central nerve but absent or fewer elsewhere, < sinus; lateral lobes up to 3 mm, scabrid, triangular or shortly awned; central awn to 15 mm reflexed from 1 mm flat or infrequently twisting column. Palea to 6.5 mm, ± = lemma, interkeels with prickle teeth above and often short hairs below. Rachilla to 1 mm, occasionally short stiff hairy. Callus to 1.5 mm, hairs to 4 mm. Lodicules to 1.5 mm. Anthers to 4.5 mm. Gynoecium: ovary to 0.75 mm, stigma-styles to 2 mm. Caryopsis to 3 mm.

2n = 42

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Plant 100-150 cm tall; leaf sheath dull, chestnut brown, often rough hairy; blade to 100cm long, tapering, very scabrid above; abaxial sclerenchyma discontinuous; epidermal silica cells dumb-bell shaped; panicle lax with branches naked below; spikelets mostly 4-5-flowered, lemma hairy on back; awn with flat and twisted basal part.

Gramen 100-150 cm altum; folii vagina parum nitida, castanea, saepe hirta; lamina usque ad 100 cm longa, attenuata, supra scaberrima; schlerenchyma abaxiale interruptum; siliceae epidermidis cellulae halteriformes; panicula laxa ramulis infra nudis; spiculae plerumque 4-5 - florae; lemma dorso pilosum; arista infra complanata tortaque.