Description from Flora of China
Calamagrostis hakonensis Franchet & Savatier, Enum. Pl. Jap. 2: 599. 1879.
Perennial, subloosely tufted from a short, knotty rhizome. Culms slender, erect or base geniculate, 30–70 cm tall, 0.5–1 mm in diam., 2–4-noded. Leaf sheaths glabrous or with caducous retrorse hairs between veins, margins ciliate, mouth auriculate, auricles shortly pilose; leaf blades flat or involute, 10–25 cm, 2–8 mm wide, adaxial surface pubescent, abaxial surface glabrous, apex acute; ligule 1–1.5 mm, obtuse or truncate. Panicle open or slightly contracted, 6–15 × 1–4 cm; branches 2(–3) per node, scabrid, usually bare below middle. Spikelets 3.5–6 mm, yellowish green or purplish; glumes lanceolate, subequal, lower glume 1-veined, upper glume 3-veined, flanks smooth, slightly glossy, midvein scabrid, apex subacute; callus hairs 3/4–4/5 length of lemma; lemma 3–4 mm, conspicuously scabrid-hirtellous, apex obtuse or denticulate; awn sub-basal, 2–4 mm, straight, included within spikelet; palea subequal to lemma; rachilla 1–1.5 mm, including hairs 2.5–3 mm. Anthers 1.5–2 mm. Fl. Jul–Aug.
Forests, streamsides, shady valleys; 600–2500 m. Anhui, Guangdong, Guizhou, Hebei, Hubei, Jiangxi, Sichuan, Zhejiang [Japan, Russia (Kamchatka, Kuril Islands, Sakhalin)].