Most of them display their flowers quite aptly. What gardeners know as Azalea is in fact a kind of rhododendron. Many people have rhododendrons in their garden or flower pot. It is the national flower of Nepal. The genus has 10,24 species.It is also the largest genus in the ericaceae.One rhododendron,Rhododendron ponticum,has become an Invasive species in North America.