The classification of Rhododendron Species
according to the
1998 RHODODENDRON HANDBOOK

In this system the genus Rhododendron is divided into subgenus groups which are divided into sections themselves and divided into subsections if necessary.

¤ The subgenus Rhododendron regroups all lepidote rhododendrons that is to say those rhododendrons which have scales.
 ¤ The subgenus Hymenanthes regroups all elepidote rhododendrons without scales.
 ¤ The subgenus Pentanthera regoups all deciduous azaleas.
 ¤ The azaleas with persistent (or evergreen) leaves are mainly regrouped in the subgenus Azaleastrum.

Most of the rhododendrons (about 1000 species) is regouped in the first two subgenus and more particularly in the sections "Rhododendron" and "Ponticum" which are divided in subsections 1 and 3.
The # 4 opens a page to the subsections "Vireyas" which are tropical rhododendrons that need protection because they die if the temperature drops below 0°C.