Tree Peonies P. Suffruticosa
Planting & Culture
In general tree peonies tend to be one zone LESS hardy than bush peonies, and are recommended for zones 5-10. (Our Rockii hybrids are much hardier, down through zones 4 and even zone 3. In hot Summer regions tree peonies need morning sun and afternoon shade. In southern regions (zone 10), without a Winter dormancy, gardeners sometimes must manually remove foliage in order to force dormancy and rebloom from season to season. Normally tree peonies arrive with leaf buds in some stage of development. Thus when first establishing your tree peony any time during the growing season, we recommend that you either place them in a protected garden area or use containers to start them in order to protect from the sudden shock of burning rays of sun in the initial stages of leaf-out. Once they are dormant you can safely move them to a sunnier spot in a permanent place and let them leaf out gradually in subsequent seasons as nature dictates. In general tree peonies grow too big to be maintained permanently in pots. The plants may become stunted over the long haul if their roots cannot expand properly. Unlike bush peonies, tree peonies should be planted with 4 - 5 inches of soil above the graft point or the root. This protects the graft from snapping off and it also suppresses "suckering" in grafted specimens. Root formation is stimulated by the extra depth, with the actual tree peony roots forming on the underground parts of the "trunk". Ideally this new root system eventually engulfs, overtakes and replaces the nurse root as the rightful, fully functional and permanent root system. You will see that actual tree peonies roots are very long, and thus require deep holes or deep pots to accommodate them, with a layer of gravel beneath the root to promote drainage . It is not good to aggressively prune roots to fit into shallower planting sites. Don’t expect an actual TREE.. Tree peonies by nature are actually woody shrubs with multiple trunks. They will spread in this manner, and can be actually sub-divided when fully established. Attempts to train them as single-trunk specimens are not recommended, will compromise the health of the plant, and definitely will limit bloom potential.
Pruning
Tree peony branches become woody and thus will respond to pruning, for purposes of shaping, thinning, and removing leggy brittle wood. This also stimulates better blooming. Bear is mind that tree peonies are slow-growing and that severe pruning might entail a long recovery time. Judicious pruning will prevent such set-backs.
Guarantee
Tree peonies failing to leaf out the following Spring are covered by our replacement guarantee, with properly documented claim. (Please list Time, place, variety, quantity purchased, and type of symptoms encountered). For online purchases we provide free shipping for replacements. If purchased at shows, you will need to pay shipping or settle for a refund of the purchase price, instead of replacement.
Hardiness
Most tree peonies are hardy down to zone 5. For climate zones down to zone 3, we recommend the "Rockii" hybrids on this site, which are wonderful, though rare and higher-priced. We also call your attention to the selections in the "Itoh" section. These are intersectional crosses between Tree peony and Bush peony types, possessing characteristics of both and possessing the hardiness qualities of the bush peony. Many unusual and rare colors are to be found in this group (such as true yellow).
Grafted vs. Non-grafted
These two propagation techniques depend upon the source. We indicate for each item whether it is grafted or root-division. There are pros and cons for each.
Grafted
Faster to establish, occasionally blooming within a year. Potentially can revert to rootstock if planted too shallow or if injured. In certain instances, especially with the Japanese grafts, the plants show a tendency to produce "suckers", which look different (red and shiny) from the regular tree peony growth, owing to the fact they issue from the rootstock, which is typically a bush peony nurse root. These suckers need to be cut off at the base. This type of Japanese graft is really fast and easy to establish and bloom, but must be managed and encouraged to produce their own real root system for their long-term survival.
Non-grafted
Generally need more than a year to bloom. No risk of reverting to rootstock or "suckering". Not so fussy about planting depth. You can readily sub-divide clumps which are on their own roots, as long as it is done during the dormant phase.