All peonies belong to Paeonia, the only genus in the family Paeoniaceae. Perennials, they are native to Asia, Europe and Western North America and flower in late spring.

There are three major kinds of peonies:

• Herbaceous peonies die back every fall.
• Tree peonies lose their leaves in the fall, but their woody stems remain.
• Itoh (intersectional) peonies are herbaceous, but their leaves resemble those of tree peonies. 

The origin of the genus name is murky, with two main theories. One is that it was named after Paeon, a physician to the Greek gods. Another possibility is that it was named after a beautiful nymph named Paeonia. 

Another myth about peonies is that they need ants in order to bloom.  Ants are attracted to herbaceous peony buds by the sugary nectar found at their base, but those ants chase away more destructive insects. The ants have nothing to do with the actual flowering process. Ants are also found on Itoh peonies but are less likely to be found on tree peonies.