Peonies are perennial flowers that come in two types: tree peonies or bush peonies. Peonies do well in areas located in USDA Plant Hardiness Zones 1 through 8. Many plants make fine companions for peonies in the garden. There are no hard and fast rules when choosing companion plants. Feel free to choose companion plants because they prefer the same soil; bloom at the same time or bloom at a different time; or to fill in colour when peonies don't bloom; or because of preferences for certain colours of flowers.
Perennial Flower Bed
Although peonies are available in early-, mid- and late-season blooming varieties, each peony only blooms for a short time, which means peonies have no colour for much of the season. Good companions for peonies are other perennials that fill in colour by blooming at different times, according to the Kansas State University Extension website. Good companions include: yarrow, which blooms from May through June and attracts butterflies; Shasta daisies, which blooming in spring and continues for several months; coreopsis and summer phlox, which bloom most of the summer; Russian sage, which begins blooming in late summer; and mums, which bloom in the fall.
Deep Rich Soil
Asters, clematis, daylilies and irises are classic perennials that make good companion plants to peonies because they all prefer deep rich soil, according to the American Meadows website . In addition, asters add fall colour because they begin blooming when mid- and late-season peonies are about to stop and many varieties of shorter asters are available for use as border plants. Clematis is a vine that can be trellised and grown behind peonies. Irises come in a variety of types and a rainbow of colours to coordinate with peonies. Daylilies begin blooming in the spring, continue blooming through the season and then produce a showy burst of blooms again in the fall, which makes them good long-term companions for peonies.
Peonies come in a wide range of colours, which makes it easy to choose companion plants based on a colour scheme. For white or yellow peonies choose an Asiatic hybrid lily in yellow, orange, pink, red, white or bicolored, suggests the North Carolina State University Extension website. Pair a red peony with any red lily, or make up your own matching or contrasting colour scheme. Along with red, white and yellow, peonies come in other colours, including cream, coral, pink and magenta.