Lackluster peonies may need to be divided in September
Q. I heard it is really hard to divide herbaceous peonies. What is the best way to plant them once I get them out of the ground?
A. Peonies are one of the few perennial flowers that prefer transplanting in the fall and September is the best time!
Peonies are a common Midwestern plant. Their history goes back to cultivation in China over 2,500 years ago. Through continued breeding programs, peony popularity has blossomed to include hundreds of improved cultivars, which have stouter, sturdier stems that do not require staking and many show good disease resistance.
How often should peonies be divided? Peonies don't require regular division for successful blooming the way many other perennials do, but there are several reasons to divide and transplant peonies.
If peonies exhibit a continued lack of flowers over several years, the cause can be too much shade as tree growth overtakes what used to be a sunny garden. Peonies are sun lovers and require six to eight hours of sun a day. Without it, the plants survive, but do not thrive. Plants may also struggle if the soil is too moist. Peonies prefer a sunny, well-drained area in your garden. Also avoid mulching peonies as it will make the soil on top of the “eyes” too deep and they will not bloom.
Begin by cutting back the stems as you would do for fall cleanup. To divide peonies, grab a spade to first dig the hole where the peonies will be placed. With a garden fork, trench around the plant at least 10 inches away from the perimeter stems of the clump.
Depending on age of the plant, the roots may be quite large and woody. With a garden hose wash off the dirt from the clump and gently use the spade or a heavy knife to divide. Make sure each division contains three to five eyes; fewer eyes may cause plants to need three to five years to bloom. The eyes actually look more like pink “noses,” which are the shoots for the next season.
Plants should be planted away from competition with trees and shrubs. To encourage air circulation, leave sufficient room between plants, allow at least 3 feet between plants on center.
The eyes should be planted only 1 to 2 inches deep, making sure the pink eyes are pointing up. If planted too deep, the plant will produce foliage and no flowers; if planted too shallow, the eyes will freeze and die back in the winter.
Press down on the soil to remove any air pockets. After planting, water well, every two weeks to allow the root system to develop before winter.
By selecting early and late season peonies, the flower period can be extended to six weeks. Peonies are long-lived plants and multiple divisions is a great way to share them with your friends and neighbors.
— Terri Passolt
• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 on Wednesdays or email northcookmg@gmail.com. Visit web.extension.illinois.edu/mg.