Description from Flora of China
Morphological characters and geographical distribution are the same as those of the family.
Paeonia is a very complex genus and many of the species are not yet well defined. A consistent taxonomic treatment will require further studies throughout the world distribution of the genus in order to resolve questions about the limits of, and relationships between, the species.
Also see HONG, D. Y. & PAN, K. Y. 2005. Notes on taxonomy of Paeonia sect. Moutan DC. (Paeoniaceae). Acta Phytotax. Sin. 43(2): 169-177.