The generic name is Paeonia and there are some 50 species in this group.
The name peony comes from Paeon, a physician in Greek mythology. His teacher was jealous of his skills as a healer and intended to murder him. The gods took pity and Pluto turned him into a flower to save him from this fate. With this start it is not surprising that there is a wealth of folklore attached to these species. The plant is alleged to relieve headaches, cure convulsions, prevent nightmares, and if placed by the door of a house it will also keep all those inside safe from evil spirits. A truly miraculous and versatile plant indeed.
There are many species of peony scattered throughout the Northern Hemisphere. No wild species are native to the eastern United States, though P. brownii and P. californica are found in the western United States.
The flower color ranges from white through yellow, pink, and red to purple. Flower size is variable from 1-10 in (2.5-25.4 cm) in diameter and they are usually produced in the early spring for six to eight weeks. A couple of the larger species (such as P. lutes) will occasionally produce flowers in the fall as well.
The majority of species are hardy shrubs up to 5 ft (1.5 m) tall. Some of the tree growth forms will reach 10 ft (3 m). All are quite long lived—an age of 50 years is not uncommon.
All peonies are beautiful and easy to grow. They will grow outdoors in Canada and all of the United States, although they will not thrive in subtropical sections of the southern states. Peonies do not like shade or poor drainage soils and they have very few problems with disease or pests. Many hybrids are produced, both naturally and artificially.