The genus Buddleja L., described by Linnaeus in 1737 in honor of Adam Buddle, has experienced multiple taxonomic reclassifications, being placed in Loganiaceae, Buddlejaceae, and currently Scrophulariaceae. Despite its ecological and cultural relevance, species delimitation and classification remain contentious, reflecting persistent challenges in defining morphological and molecular boundaries. Estimates of species richness range from 100 to 150 taxa, with Plants of the World Online recognizing 111 accepted species, nearly half distributed in the Americas. In Mexico, 14 species are reported, including Buddleja cordata Kunth (tepozán), a tree of notable cultural and medicinal importance. We reviewed classical taxonomic literature, modern systematic studies, botanical databases (e.g., POWO), and ethnobotanical records to synthesize historical classifications, nomenclatural variants, species richness estimates, and cultural associations. Our analysis confirms that Buddleja is a taxonomically complex genus, characterized by wide morphological variation in vegetative and reproductive traits, further complicated by dioecy and hybridization. Mexican species exhibit multiple vernacular names, reflecting their strong cultural recognition. While B. cordata is widely employed in traditional medicine for renal, digestive, and inflammatory conditions, other taxa are valued for ornamental and ecological functions. Overall, Buddleja exemplifies broader challenges for plant taxonomy in the 21st century. Addressing these complexities is essential not only for biodiversity conservation and ecological restoration, but also for the preservation of traditional ecological knowledge.