牛鞭草 niu bian cao

Rottboellia sibirica Gandoger, Bull. Soc. Bot. France 66: 302. 1920 ["1919"]; Hemarthria compressa (Linnaeus f.) R. Brown var. japonica (Hackel) Y. N. Lee; H. japonica (Hackel) Roshevitz; Rottboellia compressa Linnaeus f. var. japonica Hackel; R. japonica (Hackel) Honda.

Perennial, with long creeping rhizomes. Culms usually solitary at rhizome nodes, erect, 1(–1.5) m tall, ca. 3 mm in diam., branched mainly above middle, nodes conspicuous, dark, glabrous. Leaf sheaths loose, compressed, lightly keeled, shorter to longer than internodes; leaf blades linear, 15–30(–40) × 0.4–0.8 cm, rather stiff, glabrous, narrowed or subcordate at base, apex acuminate; ligule 0.5–1.5 mm. Racemes solitary or fascicled, subterete, 6–10 cm, fairly stout, articulation line horizontal, disarticulating at maturity. Sessile spikelet slightly longer than adjacent internode, 5–8 mm; callus truncate, 0.4–0.8 mm; lower glume narrowly lanceolate, leathery, flat to subconvex on back, subapically slightly constricted, obtuse to emarginate; upper glume adnate to rachis, 4–7 mm, acute; lower floret 3.4–5.2 mm; upper floret 3.4–4.3 mm. Pedicelled spikelet 5.3–9.4 mm, both glumes slenderly acuminate. Fl. and fr. Jul–Oct. 2n = 18.

Damp places, sandy beaches. Anhui, Guangdong, Guangxi, Guizhou, Hebei, Hubei, Hunan, Jiangsu, Jiangxi, Liaoning, Shandong, Zhejiang [Japan, Korea, Pakistan, Russia (E Siberia)].

This is the only species in China with terete racemes, a transverse articulation line, and a truncate callus beneath the sessile spikelet. The racemes disarticulate at maturity more readily than those of the other species. In spikelet characters it is similar to Hemarthria altissima.