Peonies are true perennials, representing a generational investment in the landscape. They are highly valued for their stunning, fragrant flowers and exceptional longevity. Peonies reliably return year after year, with some plantings thriving for over a century.
Defining Peonies as Perennials
A perennial plant lives for more than two years, returning to bloom each season rather than completing its life cycle in a single year like an annual. Peonies exemplify this trait with an impressive lifespan, often exceeding 50 years in the garden, making them fixtures in historical landscapes.
Peonies are classified into three main types based on how they return each spring. The most common is the herbaceous peony, which has soft, non-woody stems that die completely back to the ground with the first hard frost. New stems emerge from the root crown each spring.
In contrast, the tree peony develops a woody structure, functioning like a deciduous shrub. Its stems remain above ground throughout the winter, and new growth sprouts from buds on these permanent canes. The third category, the Intersectional or Itoh peony, is a hybrid cross between the herbaceous and tree types. Itoh peonies offer the wide color range and sturdy stems of a tree peony, yet they die back to the ground like an herbaceous variety. Understanding these growth habits dictates the specific care required for each type, especially concerning seasonal cleanup and pruning.
Proper Planting Techniques for Decades of Blooms
Proper location and planting technique are essential for decades of successful blooms. Peonies require at least six hours of direct sunlight each day to encourage strong stems and abundant flower production. While they can tolerate some light afternoon shade, insufficient sun is the most common reason for a lack of blooms.
The soil must be well-draining, as peonies cannot tolerate standing water, which can lead to root rot. They prefer a slightly acidic to neutral soil pH but are adaptable, provided drainage is adequate. Drainage can be improved by incorporating organic matter. Avoid planting peonies too close to large trees or shrubs, whose competitive roots will rob the peony of moisture and nutrients.
Planting Depth
The depth at which a peony is planted determines its long-term health and flowering performance. For herbaceous and Itoh peonies, the growth buds, known as “eyes,” must be positioned very close to the soil surface. Planting the eyes deeper than two inches (5 cm) below the soil line is the primary cause of a plant failing to produce flowers, a phenomenon called “blindness.”
Tree peonies require a different approach, especially if they are grafted onto herbaceous rootstock. The graft union must be buried deeply, about four to six inches (10 to 15 cm) below the soil surface. This deep planting encourages the tree peony portion to develop its own root system, ensuring the long-term vigor of the woody plant.
Year-Round Maintenance for Perennial Success
Once peonies are properly established, their year-round maintenance is remarkably simple, contributing to their reputation as low-maintenance garden plants. Water deeply but infrequently, especially during dry periods, focusing on the root zone to prevent fungal issues on the foliage.
Peonies are not heavy feeders, and excessive fertilization, particularly with high-nitrogen formulas, can promote lush foliage at the expense of flowers. A light application of a low-nitrogen fertilizer, such as a 5-10-10 blend, can be applied in the early spring as shoots emerge. An annual top-dressing of compost is often sufficient, and established plants generally only need fertilizer every few years if the soil quality is good.
Pruning and Dormancy
Pruning requirements differ based on the peony type. As soon as herbaceous and Itoh peonies’ foliage naturally begins to yellow and die back in the fall, their stems should be cut down to within a few inches of the ground. This seasonal cleanup removes potential disease spores that may have overwintered on the dead leaves.
Tree peonies, due to their woody structure, only require the removal of dead or damaged stems, and their permanent canes are left standing through winter. All peonies benefit from a period of cold dormancy, which is necessary for setting the flower buds for the following spring. Peonies rarely need division, and moving them is best avoided unless they become overcrowded or stop blooming after many years.