Plants belonging to this group have been cultivated for millennia in China, initially only as a source of traditional Chinese medicine particularly the skin of its roots (牡丹皮; mǔdān pí).

Paeonia × suffruticosa is the name used for most tree peony cultivars, but is not a naturally occurring species, so it can be regarded as the name for a man-made hybrid swarm.

Genetic analysis has shown that five species of the subsection Vaginatae together make up the parentage of the tree peony cultivars created before World War II.

In over three quarters of the almost fifty studied cultivars, the DNA of their chloroplasts is identical to that in Paeonia cathayana, indicating that this species is the original maternal parent.

Almost all of the remaining cultivars has chloroplast DNA identical to that in P. qiui, and rarely from P. ostii and partially from Paeonia rotundiloba.

In the nuclear DNA however, homology with Paeonia rockii is largest, with lesser contributions from P. qiui, P. ostii, P. cathayana and P. jishanensis.

The semi-double, lemon-yellow P. × lemoinei cultivar 'High Noon' has gained the Royal Horticultural Society's Award of Garden Merit.

[5] Cultivated hybrid tree peonies originate from China and its surrounding areas, possessing significant cultural meaning throughout Chinese history.

[6] Since its introduction abroad, a few unique cultivar groups have been bred in France, Britain, the United States, and some other countries.

Peonies are generally slow to grow and have flowers that only last briefly and are fragile under weather conditions such as wind, rain or hot temperatures.

Seeds that are harvested late or allowed to dry completely will not produce roots until the following spring and then do not send up shoots for another year.

In China, it is generally known as the "king of flowers", symbolizing honor, wealth, and aristocracy, as well as love, affection, and feminine beauty.

[11] Prior to the 2008 Beijing Olympics and 2010 Shanghai World Expo, the Chinese government again attempted to determine a national flower.

Many Chinese citizens suggested copying the practices of countries such as France, Japan, and Thailand, by selecting two national flowers.

[6] The root bark, often referred to as Mu Dan Pi or Cortex Moutan, is the main part that is used in Chinese medicine.