Peonies are long-lived flowering plants prized for their spectacular and often fragrant blossoms. They offer a wide array of visual forms, including distinct differences in structure and foliage. Understanding the physical attributes of a peony helps in identifying its type and appreciating the characteristics that make each variety unique. The appearance of the stems, the structure of the leaves, the bloom morphology, and the overall growth habit all contribute to the plant’s identity.
The Defining Characteristics of Peony Foliage and Stems
The foliage and stems provide the first clues to a peony’s identity. Peony leaves are often deeply divided, appearing as compound leaves with a three-by-three leaflet pattern, which gives the plant a lush, full appearance. In spring, young shoots frequently display a reddish or burgundy tint that transitions to deep green as they mature. Herbaceous peonies typically have thicker, somewhat glossy, or waxy leaves.
Peony stems vary in structural composition, influencing the plant’s seasonal appearance and mature height. Herbaceous peonies produce non-woody stems that emerge each spring and typically reach two to three feet. These stems are robust, though the weight of large blossoms can sometimes cause them to arch or droop. Other peony types develop woody stems that persist above ground all year, forming a permanent framework.
Categorizing Peony Blooms by Flower Form
Peony flowers are classified into six main forms based on the arrangement and transformation of their petals and reproductive parts. The Single form is the simplest, featuring one or two rows of large outer petals, known as guard petals, surrounding a prominent center of fertile stamens and carpels. This open structure resembles the wild species. The Japanese form is the first step in flower doubling, where the central stamens have transformed into colorful, narrow structures called staminodes, which usually encase their pollen.
The Anemone form continues this transformation, with the staminodes becoming wider and more petal-like (petalodes), often retaining a distinct yellow hue in the center. The visible anthers disappear, creating contrast between the central tuft and the outer guard petals. Semi-Double blooms have multiple rows of broad petals intermixed with a noticeable number of fertile stamens that remain visible.
The Bomb form features a distinct arrangement where a dense, spherical cluster of inner petals sits atop a collar of larger guard petals, creating a “ball on a platter” visual. Here, the stamens have fully morphed into inner petals, typically the same color as the guards. The most complex structure is the Full Double form, where the stamens and carpels have been almost entirely converted into petals, resulting in a dense, heavy mass of overlapping petals that forms a complete, ball-like flower.
The Visual Differences in Peony Growth Habits
The overall architecture of a peony plant is defined by its growth habit, which falls into three categories. Herbaceous Peonies are perennial; their stems and foliage die back completely to the ground each autumn. New shoots emerge directly from the underground root system in spring to form a rounded, bushy mound. They are typically the shortest type, reaching heights of two to three feet.
Tree Peonies grow as woody shrubs with permanent stems that remain intact year-round. This woody scaffold allows them to achieve a greater mature height, often reaching four to seven feet with a distinct branching pattern. Their foliage is often softer and less waxy than herbaceous varieties, and the flowers are frequently larger, sometimes reaching the size of dinner plates.
The third type, Itoh or Intersectional Peonies, are hybrids that blend characteristics of the other two. These plants possess a woody base but behave like herbaceous types, as their stems generally die back near the ground in winter. Intersectional peonies form a sturdy, rounded bush, usually shorter than tree peonies, and are noted for their strong stems that hold large flowers upright. They inherit the unique leaf form of the tree peony parentage while maintaining the perennial life cycle of the herbaceous parent.