Much like no. 37 [Polygonum cuspidatum Siebold & Zucc.]; stems angular; lvs avg larger, to 30 cm, tending to be more gradually acute, ovate with cordate base, the basal lobes broadly rounded; fls perfect; 2n=44. Native of e. Asia, rarely escaped from cult. in our range. (Reynoutria s.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.