Paeonia lactiflora, commonly known as the herbaceous or garden peony, is a perennial plant. Its growth cycle is entirely herbaceous, meaning its stems and foliage die back completely to the ground each winter. The plant survives the cold season through its underground storage organs—a cluster of thick roots and eyes (buds) from which new growth emerges in spring. In contrast, tree peonies (e.g., Paeonia suffruticosa) are deciduous woody shrubs. They possess permanent, above-ground woody stems and branches that persist year-round. While they lose their leaves in autumn, the woody framework remains, and new growth emerges from these existing stems in spring. This fundamental difference in life cycle is the primary driver for their divergent care needs.
Both types thrive in well-lit conditions but have nuanced preferences. Herbaceous peonies (Paeonia lactiflora) require a minimum of six hours of full sun per day to bloom profusely and maintain strong, sturdy stems that prevent them from flopping over. In very hot climates, they can benefit from light afternoon shade. Tree peonies, while also sun-loving, are more sensitive to intense afternoon heat. They perform best in a location with full morning sun and dappled or light afternoon shade. This protection helps prevent the scorching of their large, often delicate flowers and reduces stress on the plant during the hottest part of the day.
This is one of the most critical distinctions in their cultivation. For herbaceous peonies, correct planting depth is paramount for flowering. The eyes (pinkish-red buds on the root crown) must be planted no deeper than 2 inches (5 cm) below the soil surface. Planting too deep is a common reason for a plant to grow healthily but fail to bloom. Tree peonies, however, are grafted plants. They must be planted with the graft union—a noticeable bulge where the woody tree peony scion is joined to a herbaceous peony rootstock—located 4 to 6 inches (10-15 cm) below the soil level. This depth encourages the tree peony scion to develop its own roots and ensures the plant's long-term health and stability. Both types demand excellent drainage and prefer fertile, loamy soil with a neutral to slightly alkaline pH.
Pruning practices are dictated by their growth habits. Herbaceous peonies require minimal pruning. The entire stem structure is cut down to ground level in late autumn after the foliage has died back, which helps prevent the overwintering of fungal diseases like botrytis. For tree peonies, pruning is optional and is done for shaping, removing dead wood, or controlling size. It should be performed in late winter or early spring before new growth begins. Only dead, damaged, or very old branches are removed; excessive pruning reduces flowering. Regarding winter protection, newly planted tree peonies may benefit from a mulch layer over their root zone for the first couple of winters, but their woody stems are generally hardy. Herbaceous peonies are extremely cold-hardy and require no winter protection once established.
Both peonies are not heavy feeders but benefit from appropriate nutrition. A balanced, low-nitrogen fertilizer or one specifically formulated for roses or peonies can be applied to herbaceous peonies in early spring as shoots emerge and again after blooming. Excessive nitrogen promotes lush foliage at the expense of flowers. Tree peonies have similar needs but can be fertilized slightly earlier in spring, as their growth cycle begins sooner. A top dressing of compost or well-rotted manure around the base of both plants (keeping it away from the crown or stems) in early spring is an excellent practice to enrich the soil.
