Annual; stems weak, ascending or erect, 1–5 dm, branched from the base, many-fld; lower lvs long-petioled, ovate or lance-ovate, 1–4 cm, basally obtuse or rounded; cauline lvs progressively narrower, most of them linear, scarcely differentiated into blade and petiole; pet 1–5, 2 mm, equaling or a little shorter than the sep; stamens 10 or fewer; achenes 1 mm, very shortly beaked. Ditches, muddy ground, and shallow water, mostly on the coastal plain; s. N.Y. to Fla. and Tex., n. in the interior to Mo., Ind., and O. May, June.