Tree peonies are distinguished from herbaceous peonies by having a persistent woody stem that remains alive above ground during winter. Herbaceous peonies die down to the ground every autumn. While many varieties of tree peony remain at about the size of herbaceous peonies, some cultivars, especially American hybrid peonies, are particularly vigorous and can grow up to heights of 1.5 to 2.0 m after 10 years, considerably more imposing than an herbaceous peony. With respect to size, there has been a move in recent years to call tree peonies “woody shrub peonies” which is more accurate but more of a mouthful! In addition to size, tree peonies come in a wider range of colours, are often more vivid in colour, and can have larger flowers, some up to 30 cm (1 foot) across.

Culturally, tree peonies have similar requirements to herbaceous peonies. However, tree peonies seem to do better in warmer climates where herbaceous peonies are marginal with less requirement for winter chilling to set the flowers. Naturally for larger cultivars, more space has to be allowed for.