A genus of one species. See description under O. arboreum.
Oxydendrum has long been understood as a distinctive genus with just one surviving representative, with a natural distribution in the southern and eastern United States. It varies in habit but is too uniform in key characters ever to have been split into subspecies, varieties or formae. Its densely leafy, rather crooked habit, the shape of its leaves and in particular its showy, drooping panicles of bell-like white heather-family flowers readily suggest that its closest living allies are in the genus Pieris, though all Pieris are evergreen, and Oxydendrum itself is one of the brightest players in the fall spectacle of eastern North America. Phylogenetic analyses by Kathleen Kron et al. (Kron et al. 2002) have confirmed the genus’s position within the heather family as the sister group of the clade that includes Andromeda, Gaultheria, Lyonia and Vaccinium; Oxydendrum is now placed in its own tribe, Oxydendreae H.T. Cox.