The act of deadheading, or removing spent flowers, is a routine practice for many garden plants, but its importance for the herbaceous peony is often misunderstood. For peonies, this task is not about encouraging a second flush of blooms in the same season, as the plant is already genetically programmed for a single, spectacular display in late spring or early summer. Deadheading an herbaceous peony involves snipping the faded flower head just above the first set of healthy, full leaves below the bloom. The decision to skip this simple step sets off a chain of biological and aesthetic consequences that affect the plant’s appearance, its long-term health, and the quality of its flowers the following year.
Immediate Aesthetic Consequences
Allowing spent peony flowers to remain on the stem results in an immediate visual decline of the entire plant. The large, heavy petals of the double-flowered varieties will brown, shrivel, and often drop onto the surrounding foliage, creating a messy appearance.
The weight of these decaying, rain-soaked flower heads can cause the still-green stems to bend sharply or flop over entirely, especially in cultivars with weaker stems. If the fertilization of the flower was successful, the plant begins to form prominent, heavy seed pods that add to this downward pressure. This flopping drags the healthy foliage toward the ground, which creates a denser, more shaded environment near the plant’s crown. The overall look quickly transitions from a vibrant, upright shrub to a sprawling, untidy mound.
The Impact on Next Year’s Blooms
The most significant consequence of not deadheading a peony is the diversion of stored energy away from future flower production. A plant’s primary biological function after flowering is reproduction, which involves the formation and ripening of seeds. To accomplish this, the peony shifts its focus from storing energy to mobilizing resources for the developing seed capsules.
The seed pods act as an energy sink, consuming photosynthates—sugars produced by the leaves—that would otherwise be transported down to the fleshy root system. These roots are the plant’s primary storage organs, building up reserves of carbohydrates throughout the summer and fall to fuel the next season’s growth.
The energy stored in the roots is directly responsible for the vigor of the plant, the size of the stalks, and the initiation of flower buds for the following year. When a peony is left to ripen a full set of seeds, the drain on these root reserves is substantial. This depletion often results in a noticeably reduced bloom display the following spring, with fewer flower stalks or smaller bloom sizes.
Increased Susceptibility to Disease
Leaving spent flowers on the plant also creates a direct pathway and favorable environment for common fungal pathogens. The petals of the faded blooms, being dead organic matter, are highly susceptible to infection, particularly by Botrytis paeoniae, known as Botrytis Blight or gray mold. This fungus thrives in the cool, moist conditions that are often present within the dense canopy of a peony.
The decaying flower tissue provides a perfect starting point for the infection, allowing the fungus to produce its characteristic fuzzy gray spores. These spores can easily spread from the spent flower down the stem and onto the healthy foliage below, which is often shaded and damp from the density of the un-deadheaded plant. If the fungus successfully infects the main stem, it can weaken or even girdle the stem, causing it to collapse. Removing the spent blooms promptly is a form of garden sanitation that improves air circulation and eliminates the initial source of infection.
Intentional Reasons to Skip Deadheading
While the benefits of deadheading are clear for plant health and future blooms, some gardeners choose to intentionally forgo the practice. The most common reason is to allow the flowers to mature into seed pods for the purpose of seed collection. Growing peonies from seed is a process used by hybridizers and hobbyists interested in creating new varieties, as the resulting seedlings are genetically distinct and will not be identical to the parent plant.
For those who are not concerned with hybridizing, the developing seed pods themselves can offer a unique visual element late in the season. The pods of some peony varieties are aesthetically appealing, exhibiting interesting shapes and colors before they fully mature and split open. Allowing a few pods to remain can provide structural interest in the garden.