Description from Flora of China
Alisma plantago-aquatica Linnaeus var. canaliculatum (A. Braun & C. D. Bouché) Miyabe & Kudô.
Tubers 1-3 cm in diam. Aerial leaves with petiole 9-30 cm; leaf blade slightly falcate, lanceolate, 6-45 × 1-5 cm, 3-5-veined, base cuneate or gradually attenuate to petiole, apex acuminate. Panicles 35-65 cm, in 3-6 whorls of 3-9 branches. Pedicel 2-4.5 cm. Sepals oblong, 3-3.5 mm. Petals white, suborbicular, margin irregular. Anthers ca. 0.8 mm. Carpels regularly arranged; styles recurved, ca. 0.5 mm, stigmatose in upper ca. 1/3 of their length. Achenes obovoid, 2-2.5 mm, 1-canaliculate on back; lateral pericarp opaque, thickish. Fl. and fr. May-Oct. 2n = 28, 34, 40, 42*.
Margins of lakes, ponds, marshes, streams. Anhui, Fujian, Guizhou, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shandong, Sichuan, Taiwan, Zhejiang [India, Japan (including Ryukyu Islands), Korea].