I would like to keep my tree peony short. It is quite bushy now and about 3 feet high. Can I cut it back as I do with regular peony bushes?
Thank you for contacting the Toronto Master Gardeners. Pruning a tree peony (Paeonia suffruticosa) is done differently than pruning for herbaceous peonies (Paeonia lactiflora). Unlike herbaceous peonies which die back to the ground after the first frost, tree peonies are woody shrubs that lose their leaves in the fall but maintain their perennial woody stems. These woody stems live for about four years, and new ones sprout every year. Tree peonies grow to four to six feet high and wide, in five to ten years. Intersectional peonies (cross between herbaceous and tree peonies, eg. Itoh peonies) die back to the ground after the first frost, so they are pruned in the same way as herbaceous peonies.
Tree peonies don’t need much pruning, except to remove any dead, damaged or diseased wood, and to maintain a desired shape and size.
- Dead, damaged and diseased wood can be cut back as needed (typically in late winter / early spring) to a healthy bud or the point of origin.
- Pruning for legginess can be done right after blooming, by cutting leggy stems back by a third. Pruning for shaping and size can also be done at this time by cutting a few stems back to new buds at ground level or to about 6” high. If a lot of pruning is required, it is best to do this over a few seasons to reduce the impact.
- Spent blooms can be removed after flowering.
- Remove any suckers at the point of origin as soon as they appear. Tree peonies are usually the result of grafting a tree peony cutting onto a herbaceous peony rootstock. The rootstock often produces suckers (especially as a result of shallow planting), that you can see below the graft union, which looks like a slight bulge close to the base of the stem.
Pruning herbaceous peonies is more straightforward. Spent blooms can be removed after flowering or left in place. The foliage of P. lactiflora should not be cut down after flowering because this will inhibit photosynthesis and prevent the plant from making and storing food reserves needed for next year’s growth and flowering. In the late fall, the stems should be cut down to about an inch above the ground (about four inches for intersectional peonies) and disposed of in the garbage. This will prevent the overwintering of fungal organisms.
All the best with your tree peony !
Sept 19, 2022