Peonies are a perennial flowers prized for their large blooms and minimal maintenance. Long-lived peonies come in shades of white, pink and red, which add color to beds and borders in the landscaping. Peonies grow from shoots underground, which are actually tuberous root systems. Rot, disease and insects may damage these shoots, which becomes apparent when plants begin dying or when you divide the flowers.
Peonies form clumps of roots underground. On these clumps are buds that form the stems of the plant which produce the foliage and flowers. When part of the plant fails to produce flowers or foliage, there may be damage to the shoots underground. Weakly growing plants also may signify shoot damage. Root-rot from overly moist conditions in the soil is the most common damaging factor with peonies. Insect or disease may also be present.
Peonies only require division every 10 to 15 years and shouldn’t be divided if the plants are less than 3 years old unless shoot damage is suspected. Dig up the root clumps in fall at least 8 weeks before the first expected frost. This gives the roots time to become reestablished before entering winter dormancy. Dig around the peony clump, taking care not to hit the roots with your trowel. Dig down 8 inches into the soil then slide the trowel under the peony clump and lift it out of the ground. Brush away the excess dirt so you can examine the clumps.
Damaged roots may have obvious cuts. They may also be soft from rot or discolored from disease. While the damaged sections won’t regrow, the rest of the shoots are still viable. Cut off all the damaged parts with a clean knife or break them off with the tip of the trowel. Dispose of the damaged parts, and do not compost them, as they may harbor disease that could infect the compost. Cut apart the rest of the healthy peony shoots, leaving three to five buds on each shoot. Too few buds may lead to rot in the new root section and too many may inhibit bloom size.
Choose an area with full sunlight. Pick a bed that drains well and doesn’t become soggy. Too much moisture in the soil is the main reason peony shoot become damaged and rot. Working a 3-inch layer of compost into the bed aids drainage as well as adding nutrients to the soil. Avoid planting the root section too deeply in the bed as well. Loosen the soil to a 12-inch depth and remove it from the planting hole. Place ¼ cup of balanced fertilizer in the planting hole and refill with soil. This prevents the fertilizer from being in direct contact with the roots, which may lead to fertilizer burn and damage. Plant the root section 1 inch beneath the soil surface with the buds facing up. Water after planting continue to water only when the soil begins to dry. Too much water leads to rot.