This relatively distinct, large-flowered species occurs mostly on sedimentary rocks of diverse type in the central-southern Appalachian Plateaus (Ala., Tenn., Ky., Ohio, W.Va., Va.) and in some adjacent regions. In Ky. it is confined to acid soils on sandstones and shales, but locally frequent in some Appalachian regions. FNA 8 stated erroneously that longifolia "is restricted to limestone outcroppings and rare in all the states where it is found." The disjunct western colls. mapped here from EDMO and WARR (WKY, EKY) are somewhat distinct in having strigose upper leaf surfaces (versus thinly strigose to completely glabrous), and pubescent veins below (versus thinly hispid to glabrous). These plants might deserve variety status, but more analysis of this species across its range is needed. The disjunct population around Hot Springs in N.C. also includes relatively hairy plants (MO), and occurs mostly on base-rich soils (W). Recent analysis has suggested that two small groups of plants in Ky. form "incipient lineages" (Folk et al. 2018): (1) plants from Pine Mt. with white flowers (versus pink or green in general); (2) the plants from EDMO or WARR, with DNA data indicating a relatively close relationship to some H. americana. However, Folk et al. did not present trends in leaf pubescence that might provide further insight. They did support the distinction of southern Appalachian plants in Tenn. and N.Car., known as H. longiflora var. aceroides (Rydb.) Rosenthal, Butters & Lakela; species status may be reasonable for that taxon (W)..