Tree peonies (Paeonia suffruticosa) and herbaceous peonies (Paeonia lactiflora or other species) belong to the same genus, Paeonia, but differ in growth habits. Tree peonies are woody shrubs, with stems that persist year-round, while herbaceous peonies die back to the ground each winter, regrowing from their roots in spring.
Tree peonies develop a permanent woody framework, reaching heights of 3–7 feet. Their stems thicken over time, resembling small trees. Herbaceous peonies, in contrast, grow soft, green stems annually, typically reaching 2–4 feet. Their foliage dies back completely in autumn, and new shoots emerge from underground buds (called "eyes") in spring.
Tree peonies have deep, fibrous roots with limited storage capacity, making them slower to establish. Herbaceous peonies form thick, tuberous roots that store nutrients, enabling vigorous spring growth. The latter often require division every 10–15 years to maintain blooming, while tree peonies rarely need division.
Both types produce large, showy flowers, but tree peonies often have earlier blooms (late spring) and larger flowers (up to 10 inches wide) with a wider color range, including yellows and purples. Herbaceous peonies bloom slightly later, with flowers typically 3–6 inches wide, in shades of pink, white, red, or coral.
Tree peonies are long-lived (50+ years) but slow-growing, taking 3–5 years to flower from planting. Herbaceous peonies mature faster (2–3 years to bloom) and can live for decades but may decline if overcrowded. Both benefit from minimal disturbance once established.
Tree peonies prefer well-drained, slightly alkaline soil and tolerate more sun (6+ hours daily). Herbaceous peonies thrive in rich, loamy soil with neutral pH and need at least 6 hours of sun but benefit from afternoon shade in hot climates. Both dislike waterlogged conditions.
Herbaceous peonies are extremely cold-hardy (USDA zones 3–8), surviving freezing winters due to their underground dormancy. Tree peonies are less tolerant of extreme cold (zones 4–9) and may need winter protection in colder regions to prevent stem damage.
Tree peonies require minimal pruning—only dead or weak wood should be removed in early spring. Herbaceous peonies need cutting back to the ground in autumn to prevent disease. Both benefit from mulching to regulate soil temperature and moisture.
Herbaceous peonies are prone to fungal issues like botrytis if foliage remains wet. Tree peonies, with their elevated woody stems, have better airflow and fewer fungal problems. Both may attract ants, which are harmless and often aid in bud opening.
Tree peonies are typically propagated by grafting onto herbaceous rootstock or from seeds (which take years to flower). Herbaceous peonies are easily divided in autumn by separating tuberous roots with at least 3–5 "eyes" per division.
