The Paeonia rockii, whose Chinese name Zi ban mu dan means “tree peony with flowers with purple spots at the base of the petals”, a characteristic which makes it easy to identify and prized. It was discovered in 1925-26 by the American Joseph Rock, a plant hunter, in the Tibetan Buddhist monastery of Choni, in Gansu. The seeds were shipped to the United States and later to Europe where the species was initially called “Rock's variety”. While characteristic of Gansu, a more inland province of China, north of Sichuan and next to Tibet, it is the most widespread species also in other provinces, such as Henan and Hubei. It has a very vigorous, wide shrub, 3m tall with milky white flowers that present a characteristic black stain at the base. It grows in broadleaf forests or at the wood’s edge at altitudes of between 1,300 and 2,000 m, in shadier and wetter habitats than other species. However, it can also be found in areas that are dry in summer and very cold in winter, particularly in Gansu. It has given rise to many cultivated varieties that differ from the others for their growth pattern, elegant, characteristic foliage, the stain on their petals and their late flowering; remarkably resistant to the cold.
