Tree peonies do not really grow into tall trees, although they do have the large, showy flowers commonly seen on herbaceous peonies, but instead they have persistent, woody stems that do not die back to the ground in winter the way common peonies do. They would be more accurately called 'shrub peonies' and normally reach a height of four feet.
Most commonly grown types of tree peonies can trace their parentage back over 1400 years to ornamental garden forms of the Chinese moutan peony, Paeonia suffruticosa. According to Allan Armitage, author of 'Herbaceous Perennial Plants' the plant was first introduced in the United States in the early 1800's and "numerous references to the 'almost unknown' plants which were '...adorned by gorgeous blossoms' continued to appear in the American gardening magazines as late as 1928."
Tree peonies do require more consideration and care to become established but can be as long lived as herbaceous peonies if their requirements are met. Partial shade and a slightly basic soil are best. Most of our soils in eastern Nebraska are slightly basic so this requirement is not a difficulty.
Most tree peonies are produced commercial by grafting the desired cultivar onto a P. suffruticosa rootstock; so plant this perennial with the graft union 6-12" below the soil surface to encourage the scion, or upper portion of the plant, to form its own roots.
These plants are native to areas with very cold winter temperatures and large amounts of snow. For this reason, extra winter protection may be needed in Nebraska gardens, especially during the first few years, to prevent winter injury or winter desiccation.
All pruning of the plant should be done in the fall and be sure to remove any suckers that originate from the rootstock. Suckers will be produced most heavily during the first few years after planting.
A few cultivars worth consideration include:
'Hana-kisoi' - Large, double pink flowers.
'High Noon' - Lemon yellow flowers are red near the center, it may bloom again during the summer.
'Kamata Fuji' - The 8-inch flowers are lavender.
'Rimpo' - Dark purple flowers can be 10 inches across.
