Plant peonies in fall in well-drained soil. Choose a site that receives full sun (at least 6 hours a day) and is not close to large trees which will compete with the peonies for nutrients, water, and light. If planting specimen plants, space them 3 to 4 feet apart. In beds plant them closer so they'll fill in. Don't plant in a bed where you removed an old peony without replacing the soil as well. Peonies are long-lived, and certain diseases may build up in the soil.
Dig the holes 18 inches deep, amending the soil with a 3-inch-thick layer of compost. Set the peony plant in the hole with the "eyes" (new buds) on the top of the crown only 2 inches below the soil level. Planting any deeper may prevent the peony from flowering. Water the plants well.
Spring and Summer Care
The first spring you may only get a few flowers. This is normal as the plant is putting most of its energy into creating roots and shoots.
Fertilize. If grown in compost-amended soil, peonies require little supplemental fertilization. An annual application of compost around the drip line of the plant will be enough to keep it growing strong. If your soil is poor, add a fertilizer high in phosphorous and potassium and lower in nitrogen to promote more flowers and less leafy growth.
Mulch. Keep plants well watered and mulched with a 2- to 3-inch-thick layer of shredded bark mulch. Weed the peony bed well, keeping the mulch away from stems.
Deadhead. Remove the dead flowers to promote more leaf production and better flowering the following year. Some gardeners like to keep the dead flowers on the plant, since the seed pods that develop are interesting and artistic. If you have a well-established, healthy plant, this shouldn't deter its flower production next year.
Transplanting & Dividing
If you need to move a peony bush or have one that is flowering poorly due to overcrowding, transplant it in fall. Cut back the foliage to the ground. Dig around the outer edge of the peony clump, trying to dig up as much of the root system as possible. Move it to a new, sunny, well-drained location and set the clump in the hole no deeper than it was previously planted.
To divide the clump, remove any loose soil, and with a sharp knife cut the clump so each section has 3 to 5 eyes (buds) as well as a good root system. Set the divisions in new holes as decribed above. Keep well watered this fall.
Peonies are hardy perennials that survive cold winters with little care. If you are in a cold area, cut back the foliage after it has yellowed in fall, and mulch the base of the plant with a 2- to 3-inch-thick layer of straw or shredded bark after the ground freezes.
Tree peonies have the same rquirements as bush peonies, however they generally are less hardy. To protect them in cold areas, wrap burlap around the bushes in late fall to prevent the stems from drying out due to winter winds and cold temperatures.
With little care, your bush and tree peonies will grow and thrive, providing years of delight in your garden.