Peonies (Paeonia spp.), herbaceous perennials native to Asia, southern Europe and western North America, produce large, showy, fragrant flowers in a variety of shades during spring. Plants grow slowly at first, but can live for more than 100 years in a single location. Once planted, garden peonies begin blooming after about three years of growth. Planting container-grown plants, however, usually results in blooms the first or second year. Hardy in USDA zones 3 through 8, perennial peonies require cold winter temperatures to induce dormancy and cannot survive in the extreme southern areas of the country.
Plant perennial peonies during early fall in a location that receives full sun or light shade and has rich, loamy, well-drained soil. Apply a 2-inch layer of ground pine bark to the planting site. Incorporate into the soil with a garden tiller before planting to increase drainage.
Dig a hole in the soil about 12 to 18 inches deep and 12 inches wide. Form a cone in the center of the hole with excess soil. Spread the roots over and around the cone, and arrange them so the eyes, or reddish buds, rest no deeper than 1 inch below the surface. Cover the roots, and water immediately to firm the soil around the roots.
Stake peonies early in the season, as the large flowers retain water, causing the plants to eventually flop over under their own weight. Install wire cages around the plants to hold them up or place a stake near each one and secure loosely with garden twine.
Water peonies thoroughly once every 10 to 14 days to encourage deep rooting. The plants require no supplemental watering during winter. Soak the soil to a depth of 6 to 8 inches at each watering to ensure the root system can absorb plenty of moisture.
Feed the plants once every year during early spring, just as active growth begins. Use a complete 5-10-10 NPK slow-release fertilizer to gradually release nutrients throughout the growing season. Apply according to the directions provided on the label.
Apply a 1- to 2-inch layer of organic mulch around peonies in fall before the first frost of winter. Mulching helps insulate the roots against cold winter temperatures and also helps conserve moisture. Remove the mulch in early spring before active growth begins.
Prune perennial peonies during fall, just after the first frost of the season. Cut back any dead stems to the soil level and discard at a remote location to prevent spreading any potential diseases.