The pollination of a large mixed population ofDicentra canadensisandD. cucullariawas studied in a beech‐maple forest in southwestern Ohio. Analyses of pollinator frequencies and species, pollinator behavior, sugar components and concentrations in nectar, corbicular pollen loads carried by pollinators, spectral reflectance from corollas including ultraviolet reflectance, fragrance, blooming phenology, insect‐related fertility, and hybridization potentials suggested that these sympatricDicentraspecies are reproductively isolated by internal mechanisms but not by external barriers to hybridization. Both species were exclusively and obligately dependent upon queen bumblebees for their pollination unlike other members of the spring ephemeral flora to which they belong. The occurrence of one or both species in one area is considered primarily the result of their adaptive preference for different edaphic and possibly climatic situations and not the consequence of competitive exclusion by pollinator behavior.