List of Rhododendron species

This List of Rhododendron species includes species of the genus Rhododendron, which is in the plant family Ericaceae. Depending on the source, there are anywhere from 800 to over 1,100 wild species.[1][2] The vast majority of Rhododendron species are native to the eastern Himalaya and southeast Tibet, along with the islands of Java, Sumatra, Borneo, New Guinea, and the Philippines. The rest are broadly spread throughout the northern hemisphere in relatively small isolated populations, including Japan, northwestern North America, the Appalachian, and the Caucasus Mountains.[3]

Rhododendron has eight traditionally accepted subgenera based on morphology, still the consensus taxonomy used by most authorities:[4] Azaleastrum; Candidastrum; Hymenanthes; Mumeazalea; Pentanthera; Rhododendron; Therorhodion; Tsutsusi.[5] Hymenanthes, with approximately 225 species, and subgenus Rhododendron, with approx. 400 species, comprise what gardeners typically describe as "Rhododendrons." Two subgenera are generally known to gardeners as "Azaleas", and include many fewer true species: Pentanthera, which comprises the deciduous azaleas, and Tsutsusi, which includes evergreen azaleas.[3]

Modern cladistic analysis, based on nuclear genetics, proposes changes in the classification of species within subgenera. These proposals are based on at least three different studies, with no changes proposed within subgenus Rhododendron and its sections. The major proposed changes are: to make section Choniastrum (originally in subgenus Azaleastrum) a separate Choniastrum subgenus; to combine sections Ponticum, Pentanthera, and the species Rhododendron canadense in subgenus Hymenanthes; subgenus Azaleastrum to include the former subgenera Tsutsusi, Mumeazalea, Candidastrum, and Menziesa, along with former sections Viscidula, Azaleastrum, Sciadorhodion, and the species Rhododendron vaseyi.[4]