Peonies are classified according to flower form. All peonies have five or more large outer petals called guard petals and a center of stamens or modified stamens. Single forms have centers of pollen-bearing stamens. Flowering usually lasts one week in late spring to early summer. Flower color may be any except blue.
Peonies grow from two to four feet in height.
Support is often required for tall, double hybrids. Peonies thrive in sunny locations and well-drained soils, tolerating a wide range of soil types. Best growth is in soil with a pH range of 6.5 to 7.5, deep and rich in organic matter. They are hardy from zone 8 to zone 2, with some exceptions. Each plant requires an area about three feet in diameter.