The peony is a beloved perennial flowering plant, prized for its large, often fragrant blossoms and its use as both a showy ornamental and a popular choice for cut flowers. Peonies thrive in temperate landscapes, displaying a wide range of colors, from pure white to deep crimson. They typically flower in late spring and early summer, providing a burst of spectacular color before the plants settle into attractive green foliage for the remainder of the year.
Botanical Classification
Scientifically, all peonies belong to the genus Paeonia, which is the sole genus contained within the family Paeoniaceae. Current scientific consensus suggests there are approximately 33 recognized species within the genus Paeonia worldwide. The native geographic range of this genus is broad, spanning across the Northern Hemisphere in Asia, Europe, and parts of Western North America.
The family Paeoniaceae is characterized by perennial herbs or, in some cases, shrubby plants that grow from stout rootstocks. These plants feature large, showy flowers and are distinct enough from other flowering plants to warrant their own family.
Primary Growth Forms
Beyond their scientific classification, peonies are broadly categorized into three main groups based on their structural growth habit. The most common type is the herbaceous peony, which includes Paeonia lactiflora, often called the Chinese peony. Herbaceous varieties grow on stems that emerge each spring and completely die back to the soil level every winter, requiring cold dormancy to produce blooms. These plants are known to be extremely long-lived, capable of flourishing in the same spot for fifty years or more.
The second major category is the tree peony, which develops woody stems that remain above ground year-round, forming a small shrub. Unlike herbaceous relatives, only the leaves drop in the fall, leaving the permanent woody structure to persist through the winter. Tree peonies generally produce larger, more dramatic flowers and often bloom earlier in the season.
The third type is the intersectional peony, also known as the Itoh hybrid, which is a cross between the herbaceous and tree peony forms. These hybrids combine the strong, sturdy stems and unique foliage of the tree peony with the growth cycle of the herbaceous type, dying back to the ground in the fall. This hybrid vigor provides a longer blooming period and often introduces new colors, such as yellow, not commonly found in older varieties.
Categorizing Bloom Shapes
Peonies are further classified by the morphology of their flowers, defined by the arrangement of petals, stamens, and carpels. The classification is based on five primary bloom shapes.
- Single bloom: Features one or two rows of broad outer guard petals surrounding a fully visible center of pollen-bearing stamens.
- Semi-double form: Has multiple rows of petals, but the stamens and sometimes the carpels remain clearly visible among the petals.
- Full-double peony: The densest form, where the stamens and carpels have entirely transformed into petals, resulting in a large, globe-shaped flower with a concealed center.
- Bomb form: A variation of the double, featuring a ring of larger guard petals supporting a dense, rounded mound of shorter petals in the center.
- Japanese form: Characterized by a single or double ring of guard petals surrounding a center composed of modified stamens, called staminodes, which often appear tufted or feathery.