Despite the name, tree peonies are actually small (rarely over 6 feet tall), sparsely branched, slow-growing deciduous shrubs. Cultivated tree peonies are listed under the name Paeonia suffruticosa, which is really a hybrid group involving several wild Chinese peony species including P. cathayana, P. ostii, and P. rockii [pdf]. Records show that tree peonies were cultivated in China as long as 1,400 years ago, and centuries of subsequent breeding around the world have resulted in hundreds of named cultivars.
Tree peonies are treasured for their exquisite large flowers (often 6 or more inches wide) that may have single, semi-double, or double forms. Cultivars are available in a fabulous range of colors from white to pink, red, coral, purple, and yellow, and many are delightfully fragrant. It’s no wonder they were deemed the king of flowers in ancient China, and are still considered so today.