Calamagrostis longiflora P. C. Keng; C. venusta (Keng) Tzvelev; Deyeuxia longiflora (P. C. Keng) B. S. Sun & Y. H. Wang; D. venusta Keng.

Perennial, loosely tufted. Culms erect or geniculate at base, slender, (12–)30–60 cm tall, 1–2 mm in diam., glabrous, 2–3-noded. Leaf sheaths smooth; leaf blades flat, 3–12 cm, 2–5 mm wide, scabrid; ligule 2.5–6 mm, toothed. Panicle open, very loose, 4–15 × 2–12 cm; branches usually paired, rarely in whorls of 3–4, distant, ascending or widely spreading, scabrid, lower 1/2 bare. Spikelets 3–7 mm, yellowish brown or purple; glumes ovate-lanceolate, lower glume slightly longer than upper, 1-veined or obscurely 3-veined, scabrid, apex acuminate; callus hairs 1/4–1/3 length of lemma; lemma 3.5–5 mm, equaling or slightly shorter or longer than glumes, lateral and intermediate veins prolonged into 0.5–1.5 mm mucros with the outermost mucros longest; awn sub-basal, 5–6 mm, geniculate with twisted column; palea ca. 2/3 as long as lemma; rachilla 0.5–1 mm, including hairs up to ca. 2.5 mm. Anthers dimorphic, 0.5–0.6 mm when ovary sterile, 1–1.2 mm when ovary fertile. Fl. and fr. Aug–Sep. 2n = 28*.

Deyeuxia flavens is close to Agrostis triaristata (J. D. Hooker) Bor (D. triaristata J. D. Hooker; Calamagrostis tripilifera J. D. Hooker) from Bhutan and India (Sikkim), but that species has smooth panicle branches, a smaller floret, more pronounced mucros at the lemma apex, and a minute rachilla extension. Deyeuxia flavens lies on the boundary between Agrostis and Deyeuxia because of the short callus hairs but penicillate rachilla extension. Dimorphic anthers are also known in other species from the Himalayas, e.g., D. mazzettii, D. nivicola, and D. nyingchiensis.

* Alpine meadows, grassy slopes, open woodlands or shrublands, especially along river banks; 2700–4500 m. Gansu, Qinghai, Sichuan, Xizang, Yunnan.