Mapping here is provisional. Variation within this largely Appalachian species, broadly defined, needs further study. Even after segregation of the three new species noted here, there appear to be "typical" and "lowland" variants; see notes under the latter. Leaf width varies much within each region; some colls. (EKY, KY, MO) from BELL, BUTL, GARR, HARL and ROWA have exceptionally narrow leaves (ca. 2-3 cm wide). Moreover, there has probably been introgression with other species, especially fistulosa.