Description from Flora of China
Calamagrostis effusiflora (Rendle) P. C. Kuo & S. L. Lu ex J. L. Yang; Deyeuxia arundinacea P. Beauvois var. laxiflora (Rendle) P. C. Kuo & S. L. Lu; D. sylvatica (Schrader) Kunth var. laxiflora Rendle.
Perennial, densely tufted. Culms erect, 80–120 cm tall, 3–5 mm in diam., pubescent just below panicle and on nodes, 2–4-noded. Leaf sheaths with minute retrorse hairs between veins; leaf blades flat or slightly involute, 30–70 cm, 5–10 mm wide, adaxial surface densely pubescent, abaxial surface scabrid; ligule 1–2(–4) mm, truncate or obtuse. Panicle large, open, 20–35 × 15–23 cm; branches in whorls of 3–5, spreading, scabrid, lower part bare. Spikelets 3–4.5 mm, grayish green or purple at base; glumes lanceolate, equal, lower glume 1-veined, upper glume 3-veined, scabrid; callus hairs 1/7–1/5 length of lemma; lemma slightly shorter than glumes, apex 4-toothed; awn sub-basal, 4–5.5 mm, weakly geniculate, column slightly twisted; palea subequal to lemma; rachilla 0.5–0.7 mm, including hairs 2–3 mm. Anthers 1.5–2 mm. Fl. and fr. Jul–Oct.
Deyeuxia arundinacea var. laxiflora is not taxonomically a variety of D. arundinacea, which is a different grass; see the comment under D. pyramidalis below.
* Wet places, especially river banks; 600–2900 m. Gansu, Guizhou, Henan, Ningxia, Shaanxi, Sichuan, Yunnan, Zhejiang.