There are about 60 species of shrubs in this genus. Most are native to North America, Central America, Asia and Southeast Europe.

The genus name comes from Pharoah Ptolemy II Philadelphus (308-246 B.C.). Aristotle name a tree after him but that tree is now unknown. Later someone took the name and applied it to this species of shrubs. It has nothing to do with the City of Philadelphia, PA.