Description from Flora of China
Calamagrostis diffusa (Keng) P. C. Keng, Bull. Bot. Res., Harbin 4(3): 195. 1984.
Perennial, very loosely tufted, stoloniferous; stolons long, slender. Culms slender, decumbent, 30–80 cm tall, 1–2 mm in diam., 4–6-noded. Leaf blades flat or inrolled, 10–20 cm, 1–3 mm wide; ligule 1.5–3 mm, toothed. Panicle loose, open, 15–30 × 5–15 cm; branches paired or in whorls, up to 15 cm, very slender, flexuous, bare below middle, di- or trichotomously branched above, smooth, branchlets and pedicels capillary, drooping. Spikelets 2–3 mm, brownish purple; glumes unequal, lower glume narrowly lanceolate, 2–2.5 mm, apex acuminate, upper glume broadly lanceolate, 1.5–2 mm, apex obtuse; callus hairs equal to or slightly shorter than lemma; lemma 1.5–2.5 mm, apex obtuse or emarginate, awnless; palea 1/2–2/3 as long as lemma; rachilla ca. 0.5 mm, including hairs up to 1–1.5 mm. Anthers ca. 0.5 mm. Caryopsis oblong, ca. 1.5 mm. Fl. and fr. summer and autumn. 2n = 28*.
The name "Deyeuxia agrostioides L. Liou" (Vasc. Pl. Hengduan Mts. 2: 2240. 1994) belongs here, but was not validly published because no Latin description was provided.
* Grassy slopes, among shrubs, on wasteland; 1900–3800 m. Guizhou, Sichuan, Yunnan.