This taxon has been confused with cordata, eplingii and clingmanii, but Nelson (2008; Poindexter & Nelson 2011; W) has recently clarified its status. It is centered in the Appalachian regions of Tenn., Ky., Va., Ala., Ga., S.C. and N.C. S. nuttallii is close to cordata, which may intergrade. It has leaf blades usually elliptic-oblong with L/W ca. 2.5-3.5 (versus ovate with L/W ca. 1.5-2.5), the bases rounded to slightly cordate (versus distinctly cordate), the margins serrate to crenate (versus crenulate), and the petioles generally shorter (ca. 1-2.5 cm versus 1.5-6 cm). Also, it has a relatively stiff stem summit (versus often flexuous or lax), and it sometimes has relatively narrow calyx-lobes ("deltoid-lanceolate" vrsus deltoid) or short petioles (suggesting transitions to hispida or other species). The circumscription of S. eplingii J. Nelson has been restricted to scattered plants of mesic to hydric sites in the central Appalachians, and the species has not been confirmed in Ky. S. eplingii (sensu stricto) differs from cordata and nuttalii in its deltoid calyx lobes (versus lanceolate), more numerous flowers per vertical row (8 or more versus 6), relatively narrow leaves, and petioles only 2-5 mm. Similar plants in the Ozarks (with less glandular and more elliptic leaves) have been named S. iltisii J. Nelson (Nelson 2008).