Classification
Peonies can be classified by both plant growth habit and flower type. Plant growth types are Herbaceous (Bush), Tree, and Intersectional (Itoh).
Each flower type becomes more complex in its arrangement of petals. The flower types include Single (e.g., Athena, Dad, Krinkled White, Scarlet O’Hara, Sea Shell), Japanese (Nippon Beauty, Madame Butterfly), Anemone, Semi-Double (Paula Fay, Coral Charm, Miss America, Buckeye Belle), Double (Ann Cousins, Gardenia, Kansas, Paul M. Wild, Tourangelle) and Bomb-Double (Red Charm, Raspberry Sundae, Mons Jules Elie). Herbaceous peonies die back in winter and regrow in spring, while tree peonies lose their leaves in winter, but leave woody stems.
Intersectional (Itoh) peonies are hybrid crosses between tree and herbaceous types. They have the large flowers of a tree peony, but die back to the ground each year like herbaceous peonies.
Read more about this topic: Peony