Description from Flora of China
Pollinia japonica Miquel, Ann. Mus. Bot. Lugduno-Batavi 2: 290. 1866; Leptatherum japonicum (Miquel) Franchet & Savatier; Microstegium nudum (Trinius) A. Camus subsp. japonicum (Miquel) Tzvelev.
Annual. Culms trailing, rooting at lower nodes, up to 80 cm long, nodes glabrous. Leaf sheaths glabrous, one margin ciliate; leaf blades ovate-lanceolate, 2–5 × 0.6–1.2 cm, glabrous, midvein obscure except near base, base rounded, apex acute; ligule 0.2–0.5 mm. Racemes 3–7, very slender, slightly flexuous, lower becoming divaricate, 4–6 cm; rachis internodes filiform, glabrous, longer than spikelet; spikelets both pedicelled, shorter pedicel ca. 1 mm, longer 2.5–3 mm. Spikelets 3–4 mm; callus very shortly bearded or subglabrous in lower spikelet; lower glume narrowly lanceolate-oblong, back shallowly concave, 2–4-veined, keels scabrid, otherwise smooth, apex attenuate, hyaline, subacute or minutely 2-toothed; upper glume weakly keeled or rounded on back, apex acuminate; lower lemma lanceolate, hyaline, slightly shorter than glumes; upper lemma linear, hyaline, emarginate; awn very fine, flexuous, ca. 1 cm, apex hairlike, tangled; upper palea absent or minute. Anthers 2, 0.5–0.7 mm. Fl. and fr. Jul–Sep.
This species is very close to Microstegium nudum, but differs mainly in its pedicelled spikelets.
Mountainsides, forest margins, roadsides. Anhui, Hubei, Hunan, Jiangsu, Jiangxi, Zhejiang [Japan, Korea].