(P. canescens), a European sp. rarely intr. in our range, differs from P. argentea most notably in having some long, spreading, simple hairs on the stem, and also some long, simple hairs on the lf-veins beneath, in addition to the tomentum.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.