Peonies are perennial flowering plants belonging to the genus Paeonia, prized for their large, fragrant blooms. They are broadly categorized into two main types: herbaceous peonies and tree peonies. While both share similarities in their floral beauty, they differ significantly in growth habits, morphology, and cultivation requirements.
Herbaceous peonies (Paeonia lactiflora and related species) are non-woody plants that die back to the ground each winter. Their stems and foliage regrow from underground buds in spring. These plants typically live for decades if well-maintained.
Tree peonies (Paeonia suffruticosa and related species) are deciduous shrubs with woody stems that persist year-round. They grow taller and broader over time, with some specimens surviving for over a century. Unlike herbaceous peonies, their above-ground structure remains intact during winter.
Stems and Structure: Herbaceous peonies have soft, green stems that emerge annually from the crown. Tree peonies, however, develop thick, woody stems that branch out, forming a shrub-like framework.
Leaves: Herbaceous peony leaves are typically smaller and more finely divided, while tree peony leaves are larger, broader, and often have a leathery texture.
Flowers: Both types produce large, showy flowers, but tree peonies often have more intricate blooms with a wider range of colors and forms, including semi-double and double varieties.
Herbaceous peonies develop a fibrous root system with thick, tuberous storage roots. These roots store nutrients to support annual regrowth. Tree peonies, in contrast, have a deeper, more extensive root system with woody taproots that anchor the shrub and sustain its perennial woody growth.
Herbaceous peonies generally bloom in late spring to early summer, with a shorter flowering period of about 7–10 days per plant. Tree peonies bloom earlier in spring, often lasting up to two weeks, and their flowers tend to be more resilient to weather fluctuations.
Planting Depth: Herbaceous peonies require shallow planting, with buds (or "eyes") no more than 2 inches below the soil surface. Tree peonies are grafted onto herbaceous rootstock and should be planted with the graft union 4–6 inches below ground to encourage rooting.
Pruning: Herbaceous peonies need minimal pruning—just cutting back dead stems in fall. Tree peonies require light pruning to remove dead wood and shape the shrub, but excessive cutting can reduce flowering.
Cold Tolerance: Herbaceous peonies are highly cold-hardy and thrive in temperate climates. Tree peonies are also cold-tolerant but may need protection from harsh winds in extreme winters.
Herbaceous peonies are commonly propagated by division of the root clump in fall. Tree peonies are more challenging to propagate, often requiring grafting onto herbaceous rootstock or careful seed cultivation, which can take several years to produce flowering plants.
Both types are relatively low-maintenance but face different challenges. Herbaceous peonies are prone to fungal diseases like botrytis if conditions are too damp. Tree peonies are less susceptible to foliar diseases but may attract pests like scale insects due to their woody stems.
