By John Chapin
Peonies are garden classics that live for decades with little to no care. There are 33 known species native to Asia, Europe and Western North America. There are literally hundreds of cultivated varieties that offer big, fluffy, fragrant flowers in a wide range of colors, forms, and sizes. They thrive in Zones 2 to 8 (Central Indiana includes both Zone 5b and 6a). There are three types of peonies: herbaceous or bush, tree, and Itoh (an “intersectional” cross of tree and bush peonies). Herbaceous and Itoh peonies grow one to three feet tall and wide, while a mature tree peony can reach up to 7’ tall and 5’ wide! While bush peonies prefer full sun, tree and Itoh types planted in light shade (especially from afternoon sun) will result in the delicate crepe-paper-like blooms lasting up to two weeks. (In China, parasols are used to protect the blossoms from the sun!)
Because the three types of peonies bloom at slightly different times in spring, a carefully planted peony collection can be in bloom for up to seven weeks. Tree peonies bloom first, around Mother’s Day locally, followed by the widely planted bush varieties, blooming around Memorial Day. Finally, the intersectionals bloom in very late spring. Deer and rabbits do not find peonies palatable. However, one serious disease affects especially bush types – botrytis blight – a fungus which causes young shoots to rot, unsightly leaf spots, and deformed or stunted blossoms. There are fungal sprays that can be used, but the best action is prevention by providing lots of sun, good air circulation, removal of all infected stems, and cutting bush peonies to the ground every fall.
Although peonies can be transplanted in the spring, the survival rate is low and those that do make it may not bloom for two years or more. Fall is the better time and proper siting is crucial. All peonies hate “wet feet”, so good drainage is important. Amend the soil with compost or other organic matter if possible. Luckily for Central Indiana gardeners, peonies actually prefer our alkaline soils, but the organic matter helps both nutritionally and with drainage.
For herbaceous peonies, position peony roots (with three or more red “eyes” or buds) up to 2” below the soil surface. Too deep, and you won’t get blooms. Transplanted tree peonies should be planted at the same level as they were, but new bare-rooted plants should have the (very obvious) graft 4 to 6 inches below the ground level. Bare rooted intersectional varieties should be planted just below the surface; if potted, plant just as they are. Prune bush peonies to the ground every fall, after killing frost. Leave four to six inches of stem on your intersectionals. Tree peonies should not be pruned at all in the fall. Every spring, prune only to remove dead or damaged stems. Peonies are great garden plants, and hopefully, you will include some in your landscaping to enjoy for years and years.