This diploid (2n = 36) species is widespread across northeastern states (with little extension to Canada), mostly in dry rocky woods on base-rich soil. In contrast, its southern range includes disjunct sections in the Ozark and Ouachitas, Ky. River Palisades and Appalacbhian Cliff Section, Ridge & Valley Region, and the Piedmont. Fertile material of thsis species is generally distinct from others in section Odontotinus: cymes are relatively small (1.5-9 cm broad versus 3-14 cm) and usually eglandular; distal leaves on flowering shoots have short petioles (usually 0-0.8 cm versus 0.8-5 cm), with stipules (versus often absent), and their shape is somewhat oblong-ovate (versus often more broadly ovate to suborbicular); flowering may be generally 1-2 weeks earlier, in late April (Donoghue 1980). Vegetative material is often less distinct, with petioles up to 1.5-2 cm, but leaves still tend to be smaller (3-7 cm long versus 4-10 cm), with fewer prominent serrations on each side (6-10 versus 10-20). Var. rafinesqueanum has densely pubescent leaves, compared to the relatively glabrous var. affine; also, petioles tend to be particularly short (Cr, W). There is little overall difference in range or habitat between the two varieties, but within Ky. both are uncommon and overlap is limited. Var. rafinesqueanum occurs here on rocky slopes of limestone and base-rich shale in or near Appalachian regions. In Tenn., it is known only from a few sites in the Ridge & Valley, and var. affine is unknown (Ch; TENN). [A somewhat parallel situation exists in varieties of Lonicera dioica.] Further west, plants on the Piedmont are widespread in dry woods acros the landscape, with no concentration near outcrops (W), but dense populations have crashed in recent decades apparently due to browsing by deer (R. Peet., pers. comm,).