Erect or ascending perennial to 1 dm; stems hollow, often rooting below; lvs lanceolate to oblanceolate, to 12 cm, the lower or submersed ones commonly laciniate to pectinately parted, the upper narrower and merely dentate; pet about twice as long as the sep; mature pedicels 8-15 mm, horizontally spreading or somewhat deflexed; frs ellipsoid, straight, the body 3-6 mm, the stylar beak 1-2 mm; 2n=16, 32. Native of Eurasia, established in swamps and shallow water from Que. to Me. and Mass. and perhaps elsewhere. June, July.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.