Stems decumbent, sometimes rooting at nodes. Flowers: sepals reflexed 1 mm above base. Achene margin 0.4-1.2 mm broad. 2 n = 32. Flowering late winter-summer (Mar-Jul). Wet woods, swamps, ditches; 0-200 m; Ont; Ala., Ark., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky, La., Md., Mich., Minn., Miss., Mo., Nebr., N.J., N.Y., N.C., Ohio, Okla., Pa., S.C., S.Dak., Tenn., Tex., Va., W.Va., Wis.