Tree
peonies are small to medium-sized woody-stemmed shrubs with
several upright branches that are grown for their magnificent
flowers. The large flowered types are derived from P.
suffruticosa and the smaller-flowered types from P.
delavayi. They are long-lived shrubs but can be slow
to establish before flowering.
Plant
in fertile, well-drained soil in a sheltered spot where they
get some sun during the day and away from large trees. Grafted
plants should be planted so that the graft union is at least
10cm (4in) below the surface of the soil. In spring apply
a general purpose fertiliser and mulch with well-rotted organic
matter. Tree peonies are fully hardy but the flowers and young
foliage can be damaged by early morning sun following frost.
Tree peonies require little pruning, but in autumn lightly prune back flowered shoots to new growth below. The habit is naturally upright and older stems may become leggy. With established plants one or two older stems can be pruned to ground level in spring. Unless seed is required deadhead after flowering.
The species can be grown from seed but take about seven years to flower. Seeds of all peonies are double dormant and need two winters of chilling. After sowing in pots of John Innes Seed Compost in early autumn place outdoors. Roots emerge in the first year and seed leaves in the second. Most of the cultivars are grafted onto roots of herbaceous peony and seed will not breed true.
Tree peonies can be vulnerable to attack by peony wilt (Botrytis paeonia) especially during wet springs.