Peonies (Paeonia spp.) comprise roughly 30 species and hundreds of cultivars with varying flower colors. Broadly speaking, peonies grow as either a small woody shrub, called a tree peony, or as herbaceous perennials that die back to the ground each winter. Regardless of type, peony plants produce only one flower display each year, during mid-spring to early summer.
Peonies make pretty cut bouquets in springtime.
Precise timing of flowering varies with climate, latitude and elevation. Most peonies grow in U.S. Department of Agriculture plant hardiness zones 4 through 8. In the southern United States, peonies begin blooming as early as late March, but near the Canadian border, the same peony plant would bloom later, around late May. Local weather conditions affect flowering, too. A warmer than usual spring makes flowering begin earlier. By the start of summer, peonies complete flowering and produce seed capsules and make food in their leaves to strengthen the roots.
Even though both herbaceous and tree peony plants produce only one flower display per growing season, peonies persist for decades in the garden. Gardeners should plan on a healthy peony to endure for 30 to 50 years. Peonies develop deep roots and tend to resent being disturbed. To propagate herbaceous types or renew their vigor and flowering, plants need digging and replanting once every 10 to 15 years, according to Leonard Perry, extension professor with the University of Vermont. Peonies tend to grow less vigorously in regions with long, hot summers. Plants do best where winters are distinctly cold.
Peonies need organic-rich, fertile soils in a sunny location.
Peonies regularly produce an abundant flowering display each year. There are some factors that can inhibit or prevent flower production altogether. Planting too deeply in the soil, insufficient winter cold, too much nitrogen and lack of adequate sunlight all can make a peony disappointing to a flower gardener. A very late spring freeze may kill flower buds, too. Always plant or divide peony plants during very late summer or early fall, well after the annual flowering season is over.
A ruffle-petaled flower on a tree peony.
According to the American Peony Society, expect an individual tree peony flower to last no more than five days. Herbaceous peony flowers last longer. Excessive heat and dry garden soils can cause all peony flowers to either abort when developing or not become as large and full as possible. These conditions also shorten the flower life on plants. Once a peony flower opens, a cooler, cloudy weather regime makes the flowering display last longer.