The orange and white fringed orchids in section Blephariglottis of Platanthera subg. Blephariglottis are among the showiest terrestrial orchids in the US. Still, frequent hybridization between closely related species can make field identification difficult, and differing perceptions of species boundaries challenge a common understanding of which taxa should be considered distinct entities. In order to evaluate species boundaries in the section, we explored quantitative morphological variation within and among taxa by assessing seven floral traits in populations of five species and three putative hybrids across the eastern US from Pennsylvania to Texas. We found that floral traits generally discriminated well among taxa, albeit with some overlap for closely related taxa. Two of the hybrids displayed traits intermediate to those of their parents, whereas the third could not be differentiated from one of its parents. The data revealed considerable intraspecific variation along a north–south gradient for some taxa, which could be related to adaptation to different pollinator faunas across the distribution area. We advocate that descriptions of species, subspecies and varieties should be based on quantitative data across distribution area to cover the breadth of intraspecific variation and avoid artificial splitting due to geographically limited sampling.