Jerry Meyer, Assistant
Leonard P. Perry, Extension Associate Professor
Another species of peony that has been slow in rising to popularity in America is the tree peony. This Chinese native, also commonly referred to as Moutan, is thought to have been first discovered in an eastern province in the sixth century. It was used for medicinal purposes originally, long before it became a popular ornamental plant. It is a larger and woody relative of the much cherished herbaceous peony that graces many flower gardens.
The tree peony is distinguished most noticeably from a herbaceous peony by the fact that it retains a viable above-ground woody stem that remains after the flowers and branches have shriveled and dropped off the plant in preparation for winter: it is actually a medium-sized shrub. This woody stem should not be cut back in fall and should be pruned only if its shape is to be modified. The flower buds are much larger and flatter than those on the herbaceous peony, and are the same color as the leaves. They do not secrete honey on the bud tip. They bloom in late spring and early summer and make an excellent cutflower.
The tree peony is similar to the herbaceous peony in that it is available in single and double forms. It can reach five feet in height and almost as wide. The flowers of the tree peony, however, are usually much larger. It can be combined in the perennial border with other early bloomers like Siberian Iris (Iris sibirica), Basket-of-Gold (Aurinia), Globeflower (Trollius), Columbines (Aquilegia), Perennial Bachelor Button (Centaurea), Bleeding Heart (Dicentra), spring blooming Phlox (Phlox divaricata or P. subulata), and False Blue Indigo (Baptisia), among others, for a magnificent early season display. They also combine well with shrubs such as Lilac (Syringa), Japanese Quince (Chaenomeles) and Forsythia.
Growing a tree peony. It is an easy care plant, provided certain environmental conditions are met. They prefer to be planted away from the roots of other shrubs and trees, in a rich, deep, slightly sweet, and well-textured soil. It is important to add well-rotted cow manure or humus before planting if the soil quality is suspect. Soil should be well-drained: excessive moisture can encourage the development of fungus. If the soil is rich, the tree peony can tolerate mild drought without additional watering. To take advantage of available soil nutrients, tree peonies prefer a slightly alkaline soil. Many garden centers offer basic pH testing: call your favorite garden center to determine whether this service is provided, then bring in a small soil sample taken from the planned planting site. Tree peonies need iron, which is used by the plant to improve general vigor and depth of flower color, so it would be helpful to apply some iron sulphate, commonly available in small bags at garden centers. In northern climates, like Vermont, it helps to locate them such that they are protected from the worst of winter winds. They can be grown in full sun in the north, and appreciate a little midday respite from the sun, which can be provided by the dappled shade of nearby trees or shadows cast by buildings. Tree peonies are hardy to USDA Zone 3, so are safely grown in virtually all areas of Vermont.
Planting Bare root peonies are best planted in the fall. Potted plants found at garden centers may be planted at any point during the season, but it is best to avoid planting during exceptionally warm summers. If grown in a flower garden, they should be spaced three feet from their nearest neighbor to allow for mature growth. In preparation for the first winter, they should be given a light layer of mulch to prevent heaving from frost, critical if there is not a reliable snow cover. Some gardeners are convinced that surrounding the stem with straw and wrapping in burlap ensures better regrowth in spring, a method commonly used on roses. This may be good advice, because the flower buds can be susceptible to late spring frosts. The wrapping should only be gradually removed as springtime temperatures increase. Many people, in fact most, take their chances, choosing not to spend any time protecting their tree peonies, and have happy, healthy plants.
Once established, a tree peony should not be moved. It can live for many decades if grown in appropriate conditions. Some plantings are as old as ninety years!
Fertilizing. Fertilize a tree peony the same way you do for its herbaceous counterpart. They are very responsive to feeding, but care should be taken not to overfertilize. Use a complete fertilizer such as 5-10-5, referred to as a complete fertilizer because it contains a certain percentage of nitrogen, phosphorous, and potassium necessary for growth. Occasionally feed them additional bone meal or some form of phosphate to promote strong root development and flower set.
A few varieties to try: Many garden centers don't even offer this wonderful plant on their display tables. But through perseverance, you should be able to find them by investigating all your local garden centers and nurseries who offer a generous selection of perennials. Often, they are grouped with the herbaceous peonies, but can be easily distinguished: herbaceous peonies have smaller and much glossier leaves. Customers at garden centers may avoid the tree peonies because of the dull green leaves, not realizing that the plant they are deciding against forms much larger, showier, and more numerous flowers. Don't be surprised if they are a bit more expensive, especially new introductions. The price for a tree peony can range from $10-35.
Often, you will find tree peonies generically labeled as 'pink', 'red', etc. These make fine specimens. Here's a small list of some named varieties to try. As already mentioned, they may not be easy to find, so refer to mail order catalogs as well (Cricket Hill Gardens, CT).
'Glory of Shanghai' - glossy bright pink
'Godaiishu' - large white
'Kaoh' - large deep red
'Kinkaku' - yellow with orange edges
'Kinkoh' - large yellow
'Robert Fortune' - brilliant salmon red with fringed petals
'Souvenir de Ducher' - deep violet with reddish tinge
'Thunderbolt' - single black crimson
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Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the United States Department of Agriculture. Lawrence Forcier, Director, UVM Extension System, Burlington, Vermont. University of Vermont Extension System and U.S. Department of Agriculture cooperating, offer education and employment to everyone, without regard to race, color, national origin, sex, religion, age, disability, political beliefs, and marital or familial status.
Last reviewed 10/31/96