Commemorating Paeon, an ancient Greek physician, is said to have first used P. officinalis medicinally. Although the genus has long been considered a member of the buttercup family, Ranunculaceae, some modern botanists now place it in a family of its own, Paeoniaceae. A genus of 33 species of hardy herbaceous and shrubby perennials and a few shrubs, among the noblest and most decorative plants for a sunny or shaded border. The main division of the genus is between the herbaceous and the tree paeony, but botanically, the matter is much more complex.
Stern’s monograph, A Study of the Genus Paeonia, published by the· Royal Horticultural Society in 1946, deals with the whole classification. The wild herbaceous species are single-flowered and vary in height from about 1 foot up to 3 or 4 feet. The double varieties have been developed by breeding and selection. The tree paeonies, although woody shrubs, are deciduous and are often grown in association with other hardy perennial plants. They enjoy a sunny position but are liable to be broken by summer gales, so they should be planted in a reasonably sheltered place. Long established specimens-they live many years and attain a height of 7 feet or more with a considerable spread.
Accordingly, it is necessary to allow ample space when planting tree paeonies, for no paeony likes being moved once it has been planted. Tree peonies are often grafted onto the rootstock of P. officinalis, the common garden paeony, and when planting, care should be taken to bury the point of the union between the stock and the scion 3 inches below the surface. At this point, a young specimen may get broken in rough weather. If possible, choose a site that does not get the early morning sun because treeRead more on backyardgardener.com