Description from Flora of China
Gahnia castanea Ridley; G. javanica f. sinensis Benl.
Culms 75-120 cm tall, robust, terete, solid, nodose. Leaf sheath 10-15 cm; leaf blade usually longer than inflorescence, ca. 8 mm wide, papery to subleathery, gradually narrow apically, margin scabrous. Inflorescence a panicle, spreading and lax, consisting of a terminal and several lateral partial panicles; lateral panicles usually 2, shortly exserted from sheath; peduncles 6-10 cm. Spikelets narrowly ellipsoid, 5.5-6 mm, 1-flowered. Glumes 7 or 8; basal 3 or 4 glumes ovate-lanceolate; apical 2 glumes chestnut-brown to black, broadly oblong, shorter, 2.8-4 mm, apex ± distinctly awned and distally ciliolate; apicalmost glume with a bisexual flower. Perianth bristles absent. Stamens 3; filaments strongly elongate after anthesis; filament tips enrolled by apex of glumes. Stigmas 3. Nutlet yellowish brown with a black apex, narrowly elliptic, ca. 3.8 mm, 3-sided, smooth, shiny. Fl. and fr. Apr-Oct.
Mossy forests, thickets in dry alpine grasslands. Yunnan [Indonesia, Malaysia, Papua New Guinea, Philippines, Vietnam; Pacific islands].