Erect annual or perennial 1-8 dm, usually much-branched above; lvs lanceolate to elliptic or ovate, 1-4 cm, obtuse to subacute, broadly obtuse to rounded at base, 3-5- nerved; infl commonly widely much-branched; bracteal lvs subulate, 1-4 mm; sep linear-oblong, acute, about equaling the fr; pet 1.5-2.5 mm; stamens 5-16; styles 3, under 1 mm; fr green, ellipsoid, unilocular, 2-3.5 mm; seeds 0.4-0.7 mm; 2n=16. Wet soil; Nf. and Que. to Man., s. to Fla. and Tex. July-Sept. (H. parviflorum)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.