Much like no. 8 [Epilobium ciliatum Raf.]; erect, to 1 m, usually freely branched, ±pubescent, especially above, with short, incurved hairs, the pubescence of the stem tending to be in lines; lvs chiefly opposite, narrowly lanceolate or oblong-lanceolate, the larger often 1 dm, sharply and irregularly serrate with numerous (4-8 per cm of margin) teeth; fls numerous; cal-teeth free at the tip in bud, projecting; pet 4-5 mm, pink or white; fr 3-5 cm; seeds abruptly rounded and beakless at the summit; coma brown; 2n=36. Wet soil; Me. to Minn., s. to N.C., Ala., Ark., and Tex. July-Oct. A hybrid with no 8 has been called E. طisconsinense Ugent.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.