What is the difference between tree and herbaceous peonies?

Tree peonies are very long lived woody shrubs that grow to about 4 ft. tall and wide. They prefer a part sun location. They have long fibrous roots and woody stems.The woody branches are not cut down in fall, because they have buds formed for spring blooms. Flowers are very large and usually require no staking.They are known as Paeonia suffruticosa, though this botanical name is under question. Tree peony varieties are almost all hybrids of several species tree peonies found in China.Tree peonies do not require a freeze to bloom, but do need a winter dormancy. Herbaceous peonies are more familiar to gardeners. They are perennial plants that grow from a bulbous, fleshy root. The green stems produce long stemmed flowers which require support. In the fall, when the weather freezes, the plant dies back to the ground, but comes back faithfully every year.Herbaceous peonies need full sun, and must have a definite freezing period in winter to bloom.  more