It is common to see tree peonies more than a a hundred years old that continue to produce beautiful blossoms each year. The tree peony (Paeonia suffruiticosa), which is China's national flower, is actually not a tree, but it is considered a shrub. Unlike herbaceous (non-woody plants) peonies, these shrubs don't die back to the ground but produce woody stems. Their flowers are larger than herbaceous peonies and come in more colors including purple, yellow, green and others. Tree peonies are relatively low-maintenance, with not many problems, but they do need some regular care.
Tree peonies, which are about as wide as they are tall, can grow from 3 to 5 feet tall at maturity, taking decades to reach their final height. They need to be regularly pruned to achieve a multistemmed shrub. Some types need less regular pruning than others such as American and Chinese species that branch naturally. On the other hand, French and Japanese types require more pruning.
Time Frame and Longevity
Tree peonies have an unusual growth cycle. These plants take a long time to grow as they need at least five years for their seeds to flower. Then, it can take an additional five to eight years of growth for the flower color to stabilize.
Although peony trees are slow growers, they live long. There are some species grown in China considered to be 200 years old or more, according to the Ohio State University Extension website. Because tree peonies grow slowly and take time establish, caretakers should not just cut off pieces to be given to neighbors, as it takes as long as six to seven years before they can stand on their own.
Because tree peonies live longer than most plants, they need to be planted in the best environment. These plants need moist, well-drained, rich soils, in partial or mottled shade. Flowers last longer in shady areas, but plants bloom best in sites with plenty of sun. Tree peonies should be planted in midautumn so the plants have enough time for growing roots before the ground freezes.
Tree peonies are rarely affected by pests and the only disease that may afflict them is peony wilt. This disease first appears in early spring before flowering. Symptoms include brown, soft lesions that develop on the bottom of new shoots and buds. The wilt then becomes covered with a gray bloom. Controlling the problem involves trimming back affected shoots to healthy wood and then spraying the entire plant with a systemic fungicide that contains carbendazim.
Tree peonies need to be protected from winter winds. Ideal sites are those that have an eastern exposure. These plants are exceptionally responsive to feeding, but should not be over fertilized. The University of Vermont Extension recommends using a complete fertilizer such as 5-10-5, which has a good percentage of nitrogen, phosphorous and potassium, essential for growth.