Muhlenbergia japonica Steudel var. hakonensis Hackel ex Matsumura, Bot. Mag. (Tokyo) 11: 444. 1897.

Plants with creeping scaly rhizomes; rhizomes 3–5 cm, ca. 2 mm thick. Culms erect, 40–80 cm tall, ca. 1 mm thick at base, slender, not branching in upper part. Leaf sheaths loose, glabrous; leaf blades 5.5–12 × 0.2–0.4 cm, flat, scabrid on both surfaces and margins or abaxial surface smooth; ligule 0.5–1 mm, truncate, lacerate. Panicle 15–23 × ca. 0.5 cm, narrow, branches one or two per node, sparse, appressed. Spikelets narrowly lanceolate, 4–5 mm, gray-green; glumes 3–4 mm, papery, subequal or lower glume slightly shorter than the upper, 1-veined, scaberulous along veins, apex acuminate; lemma 4–5 mm, pale with gray-green variegation, equal to spikelet, lower 1/4 of back pubescent; awn 5–9 mm, straight. Anthers 1.5–2 mm. Caryopsis ca. 3 mm, red-brown, terete, hilum narrowly ovate, 1/3 length of the caryopsis. Fl. and fr. Jul–Oct. 2n = 40.

Wet places on mountain slopes, roadsides. Anhui, Sichuan [Japan, Korea].