List of Rhododendron 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.

[3] Modern cladistic analysis, based on nuclear genetics, proposes changes in the classification of species within subgenera.

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.