The genus Rhododendron is divided into subgenera, with different subgenera for deciduous azaleas, evergreen azaleas, lepidote rhododendrons and elepidote rhododendrons. Most Rhododendron hybrids are between plants in the same subgenus. Azaleodendrons are hybrids between plants in different subgenera. Since few crosses between different subgenera are successful, there are relatively few azaleodendrons.