Shrub to 2 m; lvs 3-7 cm, mostly broadest above the middle toothed, glabrous or nearly so; infl terminal, compound, paniculiform; fls white, seldom pinkish, 4-7 mm wide; sep spreading; fr glabrous; 2n=36. Nf. and Que. to Alta., s. to N.C., Mo., and S.D. June- Aug. Two copiously intergrading vars., widely overlapping geographically as well as morphologically:
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.