The more southern var. pubescens (E. J. Palmer & Steyerm.) Rehder, with the lower lf surfaces and young twigs hairy, extends n. to se. Va., s. O., sw. Mich., and Mo.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.