In Pennsylvania, Dodecatheon inhabits upland woods and wooded rock outcrops in the Potomac and Susquehanna watersheds, respectively. We marked 60 randomly selected plants in each of six Potomac and eight Susquehanna populations. We assessed 20 characters in these plants in flower and fruit to clarify whether they represent D. meadia or D. amethystinum, both of which had been reported for Pennsylvania. The populations differ, often significantly, in the means of all characters; but they overlap in the ranges. For example, corolla color varies from dark to pale pink in all populations. The Potomac population means are greater than the Susquehanna means in scape dimensions, flower number, floral calyx lobe length, anther length, and capsule wall thickness. In the Potomac populations, mean capsule wall thickness is intermediate between the ranges reported by previous authors for the two species. In the Susquehanna populations, this feature resembles the values reported for D. amethystinum.