Peonies are celebrated for their spectacular, fragrant flowers, but the foliage is equally significant to the plant’s overall appearance and health. The leaves are the primary indicator of a peony’s vigor, offering clues to its variety and any potential stress. Observing the size, shape, and color of the leaves throughout the year is a practical method for identification and assessing the plant’s condition. Understanding these characteristics helps maintain a robust and beautiful plant long after the blooming season has ended.
General Structure of Peony Leaves
The foliage of most common garden peonies is compound, meaning each leaf is divided into several smaller, distinct leaflets. A single mature leaf generally consists of five to nine leaflets, arranged where the leaf stalk branches into smaller segments. These leaflets are usually lance-shaped or oval, often terminating in a defined point.
The edges of the leaflets frequently exhibit minute serrations, giving the foliage a textured appearance. When fully mature in summer, the leaves display a deep, rich green color and often possess a smooth, glossy surface texture. This combination creates a dense, bushy mound that provides an attractive backdrop for other garden plants.
Peony leaves are arranged alternately along the stem, ensuring maximum exposure to sunlight. Leaflet length can range from three to eight inches, contributing to the plant’s voluminous, rounded, shrub-like habit. The sturdy structure of the leaves and stems supports the plant’s large, often heavy flowers.
How Foliage Differs by Peony Type
Foliage appearance is one of the clearest ways to differentiate between the three major groups of peonies: herbaceous, tree, and intersectional hybrids. Herbaceous peonies (Paeonia lactiflora types) produce a dense cluster of foliage with leaflets that are typically pointed and deeply segmented. This foliage grows from buds at the crown and dies back completely to the ground each winter.
Tree peonies (Paeonia suffruticosa) develop their leaves on permanent, woody stems that remain above ground year-round. Their leaflets tend to be larger, more open, and less deeply divided than those of herbaceous varieties. The overall appearance of tree peony foliage is more refined and less bushy than its herbaceous counterpart.
Intersectional peonies (Itoh hybrids) are a cross between herbaceous and tree types, resulting in a blend of characteristics. Itoh leaves often inherit the structure of the tree peony, displaying a delicate, finely divided or rounded shape. However, like the herbaceous parent, the entire plant structure, including foliage and stems, dies back to the ground in winter.
Seasonal Color Changes
The color of peony leaves undergoes distinct transformations throughout the growing cycle, which are normal indicators of the plant’s development. In early spring, when shoots first emerge, the foliage often displays striking colors like deep scarlet, bronze, or maroon, or even bright neon green on certain cultivars. This initial coloration is a natural phenomenon, not a sign of disease or stress.
As the leaves expand and mature into summer, the dark pigments recede, and the foliage settles into a stable, dark green color due to chlorophyll dominance. This deep green color is maintained throughout the summer, contributing to the plant’s lush, full appearance. The dense summer foliage produces the energy needed for the following year’s flowering cycle.
In autumn, the leaves display a final color change as the chlorophyll breaks down, revealing underlying pigments. The foliage changes into warm hues of gold, yellow, copper, and deep burgundy before collapsing. Herbaceous peonies often display the most vivid fall colors. Itoh hybrids tend to hold their form and color for a longer period late into the season.
Identifying Common Leaf Problems
Visual changes in peony leaves can signal common diseases or environmental issues, providing an opportunity for timely intervention. Botrytis blight, a frequent fungal issue, first appears as irregular brown or black spots and blotches, often starting at the margins. These spots can rapidly enlarge, causing the foliage to wilt and sometimes showing a fuzzy, gray mold on the affected tissue.
Another common fungal infection is leaf blotch, sometimes called measles, which presents as small, circular reddish-purple spots on the upper surface of the leaves. These spots can merge over time to form larger, darker purple blotches, though they usually cause only cosmetic damage late in the season. Powdery mildew is easily recognized by a thin, white or grayish coating that looks like a dusting of flour on the leaf surfaces, usually developing in late summer.
Environmental stress can cause general discoloration of the foliage, such as generalized yellowing, known as chlorosis. This symptom may indicate a nutrient deficiency (most often iron or magnesium) or poor drainage that prevents the roots from functioning correctly. Distinguishing these uniform color changes from the distinct spotting patterns of fungal disease is important for accurate diagnosis.