Paeonia rockii is a lovely tree peony that should be grown more. It can be difficult to find in a nursery, but those specializing in peonies will have it. The ones pictured here were grown from seed obtained from the Ontario Rock Garden Society Seedex program. The flowers are mostly white or light pink with dark maroon basal flares on the petals. There is some variation in flower form and coloration. One seedling from this group has red leaves in early summer.
The common name, tree peony, describes the woody stems that are produced, but it is probably more correct to call these shrubs, not trees. They do not need staking.