Much like no. 31 [Euphorbia maculata L.]; sometimes rooting at the lower nodes; lvs pale green, chiefly obovate to obovate-oblong, or narrower on the smaller branches, mostly 5-15 mm and more than half as wide, commonly widest above the middle, inconspicuously serrulate; involucre cleft on one side for fully half its length (this the most dependable distinction from no. 31); styles 0.5-0.7 mm; seeds smooth or nearly so. Moist alluvial soil; O. to Kans., s. to Ala. and Tex., and occasionally adventive farther e. Aug.-Oct. (Chamaesyce h.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.