Peonies bring big, bright blooms to the spring garden and are the first fresh flowers for the table. Their needs are simple; sun, well-drained garden soil and enough superphosphate for a good start. Really great peonies are grown by gardeners who know a few simple rules for getting the best out of this old-fashioned favorite.
Herbaceous peonies are long-lived, shrub-like perennials that bloom and die back each year; tree peonies are deciduous shrubs. Some peonies are hardy to U.S. Department of Agriculture zone 2; choose peonies grown in your area for the best results. Peonies bloom in colors from reds, pinks and purples to creams and whites. Dozens of flowers bloom on one peony bush, and by choosing hybrids that bloom at different times, bushes can bloom from the early-season irises until June's rose show gets underway.
The best time to plant peonies is in the fall, when strong roots can form for the next year's flowers. Fat tubers with three to five buds, or "eyes," will bloom within two years. Order plants in spring or summer from local growers for fall delivery; eyes should be bright red and grafted plants will grow more vigorously than plants grown from seed.
Great peonies need six to eight hours of sunlight; morning sun is best. Southern peonies may benefit from mid-day shade. Sprawling peonies need plenty of room for good air circulation; 3 to 4 feet for shrubs and 4 to 5 for tree peonies. Test your soil pH and add garden lime to raise pH above 6.0 if your soil is very acidic. Locate peonies well away from competition from shallow-rooted trees and other shrubs.
Prize peonies require well-drained garden loam that does not hold water for more that about 15 minutes. Soil should crumble when compacted in the hand and released; add compost or manure and peat moss if amendments are necessary to achieve dark, crumbly loam. Cornell's Suffolk County Extension recommends adding 1.5 cups of bone meal per bushel, or half a cup of superphosphate per bushel of dirt when planting peonies.
Plant peonies in a 2-foot-deep hole filled halfway with phosphate-amended soil. For best results, set eyes of herbaceous peonies no more than an inch or two below the surface, and the root graft line of tree peonies 5 to 6 inches below the soil surface. Water peonies well after planting; mulch for the first winter with 2 to 3 inches of organic mulch. Newly-planted peonies should begin to bloom the first or second year.
Mulch peonies each spring to control weeds and conserve moisture, but remove the old mulch each fall. Pinch extra blooms on each stem to maximize blooms. Fertilize peonies with a low nitrogen (5-10-10) food only once in the spring as growth begins. Test soil pH annually and wait to cut plants back until they turn completely brown in the fall.