Description from Flora of China
Agrostis koreana Ohwi.
Perennial, loosely tufted, sometimes shortly rhizomatous. Culms usually many, erect, 40–100 cm tall, ca. 2 mm in diam., 4–5-noded. Leaf sheaths smooth; leaf blades linear, soft, 7–8 cm × 1–3 mm, sharply scabrid on both surfaces, narrowly acuminate; ligule on tillers 2–2.5 mm, on culm leaves 2.5–4 mm. Panicle ovate in outline, 10–25 cm, remaining open after anthesis; branches 6–8 per node, widely spreading, very slender, slightly flexuous, up to 15 cm, sharply scabrid, bare in lower half. Spikelets 1.8–2.3 mm, dark purple; glumes lanceolate, equal, keel of lower glume scabrid above middle, apex acuminate; callus glabrous or nearly so; lemma 2/3–3/4 spikelet length, awnless or sometimes with awnlet up to 1 mm, apex obtuse; palea 1/2–2/3 length of lemma. Anthers 0.8–1.2 mm. Fl. and fr. Jul–Aug.
Agrostis mongolica, from Mongolia and Siberia, is very similar, but has a shorter panicle rarely exceeding 12 cm and smaller 1.5–2 mm spikelets. There is some overlap, and it is sometimes placed in synonymy under A. divaricatissima.
Riversides, lakesides, marshy meadows, often on saline soils; 500–1500 m. Heilongjiang, Jilin, Liaoning, Nei Mongol [Korea, Mongolia, Russia].