A tree peony may be any of several species of peony with a woody stem. These plants grow much larger than peonies with herbaceous stems and may reach seven feet in height. Tree peonies are relatively hardy and can produce abundant blooms in summer under ideal conditions. You'll typically start a peony tree from a cutting as they don't breed true from seed.
Select the site. Peony trees generally need as much sun as possible, although they may benefit from an hour or two of afternoon shade in an area with a hot summer. Ensure the soil is relatively neutral with a pH between 6.5 and 7.5.
Dig the hole. Loosen the soil thoroughly and ensure the hole will be large enough to accommodate the tree peony's extensive root system. Space the holes at least five feet apart if you're planting more than one tree peony.
Plant the peony tree in the fall and ensure the buds are covered by only an inch or two of soil. Fill in the hole with loose soil but ensure you pack the soil around the tree peony. Water the newly planted tree peony thoroughly and keep the soil moist but not wet.
Fertilize the tree peony. Provide the first application of fertilizer in early spring as soon as you can work the soil. Fertilize the tree peony again after it blooms in the late summer and apply fertilizer a third time in late fall.
Prune the tree peony after the first year. Remove damaged and weak branches as well as any desired shoots. Limit the stems to between five and eight per plant, and prune excess lateral buds to keep the blossoms from becoming overcrowded. This will produce fewer but larger and better flowers.