[2] The series was first classified by Diels in Die Natürlichen Pflanzenfamilien (Edited by H. G. A. Engler and K. Prantl) in 1930.

It was further expanded by Lawrence in 'Gentes Herb' (written in Dutch) in 1953.

[2] In the wild, all the species are located on soils on slopes with good drainage.

[4][1] They can be grown in large clay pots in the UK, to be able to protect them in the winter.

[2] They come from the west coast of USA, native to California, Oregon, and Washington.