In China, the cultivated tree peony is known as the King of Flowers, while in ancient Greece the herbaceous peony was dubbed the Queen of Herbs--a reminder that the genus "Paeonia" has been one of the most important and popular groups of plants in the world for millennia, coveted in East and West alike for both its ornamental and medicinal purposes. This fully up-to-date monograph contains a comprehensive taxonomic revision of the genus based on extensive field observations, population sampling, examination of a large quantity of specimens, and statistical analysis of characteristics. The book's taxonomic revision has resulted in the recognition of thirty-two new species, which will make it an essential volume for plant taxonomists and horticulturalists, as well as more adventurous gardeners.