Peonies with overcrowded roots sometimes fail to bloom, or bloom poorly. Divide crowded peonies in the fall when temperatures begin to cool. Divided peonies come into full bloom again in a season or two.
Cut the plant back to 4 inches above the soil, then dig around the roots carefully to keep as many tubers and roots intact as possible. Dig about 8 inches deep, then slide the shovel or garden fork under the roots and pry upward. Remove loose soil by gently shaking the clump.
Cut the clumps apart with a sharp knife so that each division has three to five eyes and a good portion of roots. Replant as soon as possible.
Replant clumps so that the eyes are an inch or two below the soil’s surface. Peonies planted too deeply bloom poorly or not at all. Space the plants 4 to 5 feet apart. After planting, water well and apply a 2- to 3-inch layer of mulch.