Peonies are long-lived, herbaceous perennials celebrated for their large, fragrant spring flowers. They often grow into substantial clumps over many years. When mature peonies become overcrowded or show a reduction in their annual bloom count, gardeners seek ways to refresh them. These plants can be propagated and rejuvenated through division. This article outlines the steps required to successfully divide and replant a mature peony, ensuring its continued health and vibrant blooms.
Determining the Right Time for Division
Division creates new plants from a mature specimen and reinvigorates older clumps that are sparse or shy to flower. After a decade or more, the central root mass can become woody and congested, which reduces the plant’s vigor and flower production. Separation allows the gardener to discard the old center and focus on replanting the younger, more robust outer sections of the root system.
The timing for this procedure is specific for common herbaceous peonies (Paeonia lactiflora). Division must occur in late summer or early fall, typically September through October, when the plant is entering its natural dormancy period. Attempting division during active growth will severely stress the plant, often leading to failure. Tree peonies (Paeonia suffruticosa) are rarely divided by this method, instead being propagated through grafting.
Preparing and Executing the Division
Preparation begins by cutting all the peony foliage down to a few inches above the soil line after the leaves yellow in the fall. This removal minimizes water loss and makes handling the large root mass easier. The entire clump must be carefully excavated using a sturdy garden fork placed several inches away from the plant’s crown to avoid damaging the roots.
Lifting the substantial root ball requires care to prevent snapping the thick, tuberous roots or the delicate crown where new growth emerges. After the clump is out of the ground, wash away all the soil, often using a strong jet of water. Removing the soil is necessary to expose the crown and clearly identify the small, pink or red growth buds, known as “eyes.”
The “eyes” are the embryonic shoots for the following year’s stems and flowers. The mature clump must be sectioned using a sharp, sterilized knife, heavy pruners, or a specialized root saw. Each viable division piece must contain a minimum of three to five healthy, visible “eyes” attached to a sufficient mass of fleshy root tissue to support its future growth.
Smaller divisions with fewer eyes can be created for propagation but will take longer to establish and reach blooming size. Any sections of the root mass that appear woody, soft, diseased, or are devoid of new “eyes” should be discarded. The goal is to create several robust, smaller sections from the single parent plant.
Essential Steps for Successful Replanting
Before replanting the divisions, the new site should be prepared with well-draining soil that receives at least six hours of direct sunlight daily. Peonies are heavy feeders, so incorporating organic matter, such as compost, into the planting hole will provide the necessary nutrients for root establishment. Proper drainage is important because the fleshy roots are susceptible to rot in waterlogged conditions.
The planting depth of the crown determines whether a peony will bloom after division. The “eyes” must be positioned close to the soil surface, ideally no more than one to two inches below ground level. Planting too deeply is the main reason peonies fail to produce flowers, resulting in a healthy plant that only produces foliage, a condition known as being “blind.”
Once the division is positioned correctly, the soil should be gently firmed around the root mass, ensuring no air pockets remain that could dry out the roots. A thorough initial watering helps settle the soil and hydrate the new root system. For regions experiencing severe winter cold, a temporary layer of mulch can be applied after the ground freezes to prevent the newly planted roots from being heaved out of the soil by freeze-thaw cycles.
Gardeners should manage expectations regarding immediate flowering. A peony uses the first one to three years following division to establish a robust new root system. This period means that the newly planted divisions will likely not bloom during their first spring. Patience is required, as the plant must fully recover from the physical shock of separation and regain its strength before it can support the energy demand of producing its characteristic large flowers.