It has over 100 species distributed around Southeast Asia, India, north to Japan, south to Australia and the Pacific Islands.

[2] Many species have been planted around the world for the aesthetic value of their bright purple flowers.

Species in this genus are native to temperate and tropical Asia, Seychelles, Pacific and Australasia.

[1] Several have the capacity to become invasive species, in Hawaii and other areas.

As of November 2020[update], Plants of the World Online (PoWO) accepted the following species.