B. ferulaefolia is recognized as a species consisting of 3 varieties (B. ferulaefolia var. ferulaefolia, B. ferulaefolia var. foeniculifolia and B. ferulaefolia var. ludens) widely distributed from southwestern USA through Mexico and into Guatemala. Separation of these taxa was based on several highly variable morphological characters, i.e., achene length, awn number and degree of leaf dissection. These taxa were studied utilizing field and herbarium material, morphological data, cytotaxonomic studies, greenhouse and hybridization experiments, and comparative flavonoid chemistry. Three species should be recognized: B. ferulaefolia, B. carpodonta and B. longistyla. B. ferulaefolia occurs in disturbed habitats on the high plateau from Guanajuato in southcentral Mexico northwest into the foothills of the Sierra Madre Occidental in Chihuahua in northern Mexico. B. carpodonta inhabits disturbed areas in mountain valleys or on high plateaus, while B. longistyla is found in mountain valleys on gypsum and limestone outcrops, in the Sierra Madre Oriental of northeastern Mexico in the states of Nuevo Leon and Coahuila. Morphological characteristics based on quantitative and qualitative features, such as style branch lengths and presence or absence of a red pigment in the flowering heads, are useful for distinguishing the 3 taxa. Cytotaxonomic data for these 3 spp. show that B. ferulaefolia has a chromosome number of n = 10, while B. carpodonta and B. longistyla are both n = 12. Hybridization experiments at the intra- and interspecific levels confirmed that each species is reproductively isolated from the other 2. Flavonoid comparisons of leaf and floral tissues from B. ferulaefolia, B. carpodonta and B. longistyla establish the presence of species-specific compounds that allow for the chemical separation of these 3 taxa. The 2 varieties previously recognized (B. ferulaefolia var. foeniculifolia and B. ferulaefolia var. ludens) are placed in synonymy with B. ferulaefolia, whereas B. carpodonta and B. longistyla are distinguished as species. The geographical distribution formerly attributed to B. ferulaefolia was examined and involves a number of related species.