Image courtesy of Monrovia
Itoh peonies, which are crosses between herbaceous peonies and tree peonies, grow well over a wide range of climates and feature stunning foliage, giant blooms and a bounty of available colors. Hardy in Zones 4-9.
Dig into the fabulous beauty of the Itoh peony, and you’ll encounter an inspiring story of perseverance. An Itoh peony is the result of a cross between an herbaceous peony (Paeonia lactiflora), the common garden peony, with the striking tree peony (Paenoia suffruticosa). For years, the plant world longed for a successful cross of these distinct peony types, but most plant breeders felt this was impossible because these two peonies have very different parents.
A Japanese plantsman, Toichi Itoh, devoted himself to achieving this cross. This quest became Itoh’s lifework, and he achieved his goal in 1948, crossing the herbaceous peony (Paeonia lactiflora ‘Kakoden’) with the tree peony (Paenoia x lemoinei). That successful cross produced 36 plants. Nine of those plants showed tree peony characteristics and became known as Itoh Hybrid peonies or Itoh peonies. Sometimes you’ll hear of intersectional peonies or intersectional hybrids. These plants are types of an Itoh peony.
When the Itoh peony was first introduced to the nursery trade and made available to the public, there were so few available that the price ran over $1,000 for one plant. This high price tag reflected the time required to grow these plants to the point that they could yield divisions. Today, Itoh peonies are multiplied more quickly through tissue culture techniques, bringing the price down to less than $50 to $100 per plant.
An Itoh peony is worth any price you have to pay, because these plants produce leaves and flowers that resemble tree peonies on a plant that behaves like a perennial. The plant dies back to the soil each year with the arrival of frost, and new growth emerges from soil each spring. This eliminates the worries of a late spring frost damaging flower buds on woody stems, which can occur with a tree peony.
An Itoh peony’s flower buds open to reveal large, tree peony-type blooms—dinner-plate size in many different hues, including golds and yellows, colors not readily available among the herbaceous peony types. The plants have stout stems similar to a tree peony, so there’s no need to stake plants, even though the flower heads are so large. A mature Itoh peony can produce up to 50 flowers in the course of a growing season.
Itoh peonies typically start flowering while herbaceous peonies are blooming, but the Itoh peony group reaches its peak bloom time as the herbaceous peonies are finishing. Many Itoh peony plants produce flowers from secondary buds that form below the first flower, resulting in a strong, long flower show. Each Itoh peony plant can flower for a luxuriously long window of three to four weeks.
In the garden, Itoh peony hybrids are deer-resistant and boast strong disease resistance to powdery mildew, which plagues herbaceous peonies, and botrytis blight, which commonly attacks tree peonies. Like its peony parents, the Itoh peony group offers blossoms that make wonderful cut flowers. Itoh peonies typically grow 2 feet tall and 3.5 feet wide.