五棱水葱 wu leng shui cong

Scirpus trapezoideus Koidzumi, Bot. Mag. (Tokyo) 39: 26. 1925; S. erectus Poiret var. triangularis Honda; S. juncoides Roxburgh var. triangularis (Honda) Ohwi.

Rhizomes short. Culms tufted, erect, 40-70 cm tall, ± slender, 3-5-angled, clothed at base with bladeless leaf sheaths. Leaf sheaths pale brown at base, to 12 cm, oblique at mouth. Involucral bract 1, erect, culmlike, 5-15 cm. Inflorescence a pseudolateral head, with 2-9 spikelets. Spikelets sessile, pale rust-colored brown, oblong-ovoid to ovoid, 8-14 × 4-6 mm. Glumes pale rust-colored brown, broadly elliptic, 3-4 mm, thinly leathery, with a green costa excurrent into a mucro, apex acute. Perianth bristles 6, ca. 2/3 as long as nutlet, retrorsely scabrous. Stamens 3; anthers 1.2-1.5 mm. Style ca. 3 mm; stigmas (2 or)3. Nutlet blackish brown, broadly obovoid to subspherical, ca. 2 mm, biconvex or unequally biconvex, obscurely wrinkled. Fl. and fr. Aug-Oct.

Wet places, swamps by streams; 200-1000 m. Fujian, Guangxi, Hebei, Jilin, Shandong [Japan].