Description from Flora of China
Gahnia javanica Zollinger & Moritzi var. penangensis C. B. Clarke; G. penangensis (C. B. Clarke) Kükenthal.
Culms ca. 90 cm tall, robust, terete, rigid, noded. Leaf sheath blackish brown, 8-15 cm; leaf blade equaling or slightly longer than inflorescence, 8-12 mm wide, papery to leathery, margin scabrous, apex acuminate. Involucral bracts usually shorter than inflorescence. Inflorescences black, 40-70 × 6-15 cm, spreading and lax, consisting of a terminal and several lateral panicles. Spikelets blackish, in clusters of 2 or 3 or solitary, oblong, 4-5 mm, 2-flowered. Glumes 7 or 8, blackish brown, rigid; basal 5 or 6 glumes ovate to ovate-elliptic, 2-3 mm, keeled, empty, apex mucronate; apical 2 glumes broader, bearing a bisexual flower and next a functionally male flower, margin ciliolate, apex obtuse. Perianth bristles absent. Stamens (2 or)3; filaments scarcely elongate after anthesis, sticky tips of filaments of bisexual flower cohering with tips of basal male flower. Stigmas 3. Nutlet reddish brown, ellipsoid, ca. 3 mm, 3-sided, smooth, shiny. Fl. and fr. Aug-Sep.
Moist hills and slopes; 800-1500 m. Fujian, Guangdong, Guangxi, Hainan [Indonesia, Japan, Malaysia (Peninsular), Vietnam; Australia].