Herbs perennial, 30 ~ 80 cm tall. Rhizome terete, transverse, brownish red or purplish red, nodular, with annular membranous scales at nodes, rooting at nodes. Stem tufted, erect. Leaves 2 columns; Sessile; Leaf blade narrowly linear-lanceolate, 15 -- 30 cm long and 1.5 -- 2 cm wide, apex acute, base tapering, entire or with inconspicuously sparsely obtuse teeth, glabrous on both surfaces; Leaf sheath open, cauline.