Cymbopogon annamensis (A. Camus) A. Camus

This species is taken here in a broad sense to include all slender, narrow-leaved specimens from S China and Indochina with a flat, grooved, winged sessile spikelet and a swollen lowermost pedicel. The differences from Cymbopogon caesius (Nees ex Hooker & Arnott) Stapf, from E Africa to India, are very slight. Cymbopogon caesius tends to have a longer ligule, to 4 mm, and paler inflorescences. Likewise, C. annamensis hardly differs from C. mekongensis, except in the swollen lowermost pedicel.

Perennial. Culms tufted, wiry, up to 1 m tall. Leaf sheaths glabrous; leaf blades linear or linear-lanceolate, glaucous, 10–30 × 0.5–1 cm, glabrous, margin scabrid, base rounded, apex filiform; ligule 0.5–1.5 mm. Spathate panicle narrow, lax, 6–20 cm; spatheoles reddish brown, 2–2.5 cm; racemes reddish brown to purplish, 1.5–2 cm; rachis internodes and pedicels white-ciliate on margins; pedicel of homogamous pair swollen, barrel-shaped or broadly columnar, shiny, fused to internode at base. Sessile spikelet oblanceolate, 3.6–4.5 mm; lower glume flat, deeply grooved below middle (appearing as a line or keel on inside), keels winged above middle, veinless or obscurely 2-veined between keels; upper lemma deeply 2-lobed; awn ca. 1.6 cm. Pedicelled spikelet 3.5–4 mm.

Open forests, forest margins. Yunnan [Laos, Thailand, Vietnam].

Cymbopogon martini (Roxburgh) Will. Watson var. anna-mensis A. Camus, Bull. Mus. Natl. Hist. Nat. 25: 670. 1919; C. bassacensis A. Camus.