Its closest relative is Rhododendron vaseyi from the Appalachian Mountains, which differs in having 7 stamens.
Rhododendron | rhododendron | Rhododendron ponticum | Rhododendron tomentosum | Rhododendron luteum | Eozoon canadense | American Rhododendron Society | Rhododendron vaseyi | Rhododendron subg. Hymenanthes | Rhododendron selense | Rhododendron rex | Rhododendron neoglandulosum | Rhododendron ferrugineum | Rhododendron aberconwayi | MV ''Rhododendron'' | MV Rhododendron | Maianthemum canadense |