Description from Flora of China
Andropogon flexuosus Nees ex Steudel, Syn. Pl. Glumac. 1: 388. 1854; A. nardus Linnaeus var. flexuosus (Nees ex Steudel) Hackel.
Perennial from a short stout rhizome. Culms robust, up to 3 m tall, 1–2 cm in diam., nodes glabrous or pubescent. Leaf sheaths glabrous, auricles often present; leaf blades linear, up to 100 × 1.5 cm, scabrid, abaxial surface tomentose at sheath junction, adaxial surface pilose at base, otherwise glabrous, base gradually narrowed, apex filiform; ligule 2–5 mm. Spathate compound panicle very large, lax, decompound, grayish green, up to 60 cm or more, nodes bearded, branches numerous, drooping; spatheoles 1–2 cm; racemes 1–1.7 cm; rachis internodes and pedicels ciliate on margins; pedicel of homogamous pair not usually swollen. Sessile spikelet narrowly elliptic-oblong, 4–4.5 × 0.8–1 mm; lower glume flat or shallowly concave, usually slightly transversely wrinkled, sharply 2-keeled throughout, keels narrowly winged, wings 0.1 mm wide or less, obscurely 3-veined between keels; upper lemma awned; awn 0.8–1 cm. Pedicelled spikelet 3.5–4 mm. Fl. and fr. summer to autumn. 2n = 20, 40.
This grass is cultivated in tropical regions for "oil of lemon grass." It is thought to be native to India, but is now widely naturalized in Indonesia and elsewhere. It is usually easily recognizable by its very large compound panicle of drooping branches, with numerous short, deflexed racemes of small, narrowly winged spikelets. In Bhutan and NE India the branches are looser with more widely spaced raceme pairs than usual, approaching Cymbopogon pendulus in habit. This form has been recognized as C. flexuosus var. sikkimensis Bor.
Grassy slopes; below 1000 m. SW Yunnan [probably native to India; naturalized in Indonesia, Malaysia, Myanmar, Nepal, and Thailand].