Peonies are highly valued perennial flowers, cherished for their impressive blooms and remarkable longevity. They often survive for fifty years or more in a single location. Gardeners frequently wonder about the growth pattern of these classic flowers and whether they will aggressively take over garden space. Understanding their growth habit is essential for long-term placement planning.
The Growth Habit of Peonies
Peonies do not spread invasively throughout the garden; they are classic clump-forming perennials. Unlike plants that use underground runners, peonies grow from a central structure called a crown. This crown sits at or just below the soil line and is connected to a network of thick, fleshy storage roots. The entire plant remains anchored in the same spot, expanding its size outward very slowly over many years.
The three main types of peonies—Herbaceous, Tree, and Intersectional (Itoh)—all share this non-spreading growth structure. Herbaceous peonies die back to the ground each winter and regrow from the crown in spring. Tree peonies develop woody, persistent stems. Despite their different appearances, none of these peony types exhibit the aggressive, traveling root systems associated with invasive spreaders.
How Peonies Increase in Size
When a peony appears to be “spreading,” it is actually undergoing a slow, contained expansion of its central crown. The crown naturally matures over time, gradually producing more small growth buds, often referred to as “eyes.” Each eye has the potential to develop into a new stem and flower stalk. This process leads to a denser, more robust plant with a greater number of blooms each season.
The perimeter of the peony clump expands at a very gradual pace, often only one or two inches annually. This slow growth contributes to its reputation as a long-lived specimen that should not be moved frequently. A mature herbaceous peony can eventually reach a width of three to five feet, achieved through decades of slow, outward growth. Peonies are meant to be a permanent fixture, remaining in their original planting spot for many decades.
Propagating Peonies Through Division
Since peonies do not naturally multiply, gardeners must manually intervene to create new plants from a mature clump. This process is called division and is the primary method for propagation. Division is also performed on older plants to help rejuvenate them if they become overcrowded or stop flowering well. The optimal time for dividing and transplanting peonies is in the late summer or early fall, typically four to six weeks before the first hard frost.
The process involves carefully digging up the entire root ball and washing away the soil to expose the eyes on the crown. A sharp knife is then used to cut the clump into sections. Each new division must contain three to five prominent eyes and a healthy portion of the fleshy root system. Divisions with fewer eyes may take several extra years to produce substantial blooms.
After dividing, the new plants must be placed in the soil at a very shallow depth for successful flowering. The eyes must be positioned no more than one to two inches below the soil surface. Planting them too deeply is the most common reason a peony fails to bloom.