Peony shrubs, or tree peonies, are one of several types of the plant, but they are quite different than other cultivars. Peony shrubs have wooden stems and do not die back like other peonies do. Peony shrubs also produce larger flowers and are available in more colors than herbaceous peonies. Blooms are available in yellow, white, red, pink and purple, among others. The flowers also tend to last longer than in herbaceous varieties.
Peony shrubs can live for decades. In fact, may tree peonies will outlive their owners. In China, where peonies originated, they plants are revered for both their beauty and longevity.
Because peony shrubs live so long, it's important to choose the right site. Peonies need a rich and well-draining soil. They also like a lot of sunlight. However, keep in mind that plants that get some partial shade will likely produce longer-lasting flowers. Peony shrubs can be grown in areas up to USDA hardiness zone 4, but in colder climates they will do best when they get some protection from the cold. Try planting them along the east side of a building.
If you are planting a bare-root peony shrub, plant it in the fall. Container-grown peonies can be grown in the fall or early spring. Don't plant peonies in the summer because the heat can make it hard for the plant to acclimate. If you are planting a bare-root peony, dig a hole 4 inches to 6 inches deep. Container peonies should be planted at the same depth they were originally grown.
If you want to fertilize your peony shrubs, use a 5-10-10 fertilizer and apply it in the spring, when the stems are between 2 inches and 3 inches long. You also may want to mulch around the plants each spring to prevent weed growth. Tree peonies should not be pruned in the fall.
Peony shrubs do not typically produce flowers for a few years. Plants bought at a nursery may be old enough to flower when they are purchased, but if you buy a younger shrub it may be a few years before you get blooms. When your peony begins to flower, you should remove the blooms once they begin to fade. This will help the plant preserve its nutrients.