Peonies are celebrated garden plants, often living for decades and producing spectacular, fragrant blooms each spring. The success of these long-lived perennials rests almost entirely on the depth at which the root crown is set during planting. Planting peonies correctly is the only way to avoid the common disappointment of a plant that produces lush foliage but no flowers.
Preparing the Planting Location
Selecting the right spot for a peony is the first step toward a lifetime of blooms. Peonies require at least six to eight hours of direct sunlight each day to support the energy demands of their large flowers. Good air circulation is also important, as this helps prevent fungal diseases that can afflict dense foliage.
The planting hole should be dug significantly wider than the root mass, aiming for about 12 to 18 inches across. Loosening the soil around the planting area encourages the large, fleshy roots to spread quickly. Peonies thrive in well-drained soil and will rot in consistently wet conditions, so amending heavy clay with compost or other organic matter is necessary to improve drainage.
The Critical Depth for Bare Root Peonies
The critical detail for bare-root peonies centers on the small, reddish or pink buds, often called “eyes,” located on the root crown. These eyes are the growth points that will develop into the stems and flowers for the coming season. For the plant to flower, these eyes must be planted no more than one to two inches below the soil surface.
This shallow planting depth is necessary for a process called vernalization, or winter chilling. The buds require exposure to cold temperatures, typically between 32 and 40 degrees Fahrenheit, for a specific duration to break dormancy and initiate flower development. Planting the eyes too deeply insulates them from the necessary cold, causing the plant to produce only leaves, a condition known as being “blind.”
Gardeners in warmer climates, such as USDA Zone 8, should aim for a shallower depth, with the eyes barely covered by one inch of soil. In colder regions, planting closer to the two-inch mark provides a buffer against soil heaving during freeze-thaw cycles. Carefully position the root mass in the hole with the eyes pointing upward, then gently backfill the remaining space with soil.
Adjusting Planting for Potted Peonies and Transplants
When planting a peony purchased in a container, the critical depth guideline shifts slightly. The goal is to maintain the crown’s existing soil line relative to the surrounding garden soil. Ensure the top of the root ball is level with the soil surface, planting neither deeper nor shallower than it was growing in the pot.
Transplanting an established peony requires care, as disturbance often results in the plant failing to bloom for several years. If you must move an existing plant, replant it at the exact same depth it was growing previously. Moving the crown up or down from its original position can shock the plant and restart the process of establishing flowering capacity.
Immediate Care After Planting
Once the roots are in the ground, water the area thoroughly and deeply. This initial watering helps settle the soil around the root mass and eliminates air pockets that could dry out the roots. After the soil has settled, avoid applying synthetic fertilizer during the first year, as the plant’s energy should be focused on root establishment rather than top growth.
The use of mulch requires a specific technique to prevent unintentionally mimicking deep planting. While mulch helps regulate soil temperature and retain moisture, it must not be piled directly over the crown or the eyes. Keeping the crown clear of mulch prevents the buds from being buried deeper than the prescribed two inches, ensuring they receive the necessary winter chilling. Mark the planting location with a stake, as the plant will die back completely in the fall, leaving no visible sign of its location until spring growth begins.