Tree peony sprawl is common
Cutting old, bare stems helps, although feel free to experiment
Q
A tree peony that I’ve had in my garden for around six years has become overgrown and sprawling. I’m wondering whether it can be reshaped into a more compact form. This would require a major cutting back.
A
This is a common issue with tree peonies. Over time, the shrubs have a habit of developing bare, leggy stems, which can become a nuisance if they take to leaning over a pathway or onto nearby plants. The remedy is to cut these old, bare stems to the ground. If they are all bare and leggy, cut only some of them down each year, in autumn or late winter.
Removing an entire overgrown stem is considered preferable to shortening it by cutting into old woody growth, though as an experiment I have done this with one of my tree peonies. In early summer, after the plant had bloomed, I made the cut right over a node (bump) that indicated a point or origin for potential growth. I chose a node that pointed upward to correct the lean of the long stem.
It worked. New, upright growth developed to reshape the shrub; however, my tree peonies are seed grown (Paeonia lutea). Purchased hybrid varieties may not sprout from old wood so well. You might consider experimenting on one of the least conspicuous bare stems on your plant. If it doesn’t regrow, you can always cut it to the ground.
If you decide to tidy the plant by removing a long, bare stem or two, clean up around it afterward and apply a nourishing compost mulch layer to help encourage the production of new stems.
Though the plants do well in a fertile, humus-rich, moist soil, to keep growth as sturdy and compact as possible take care not to over water or overload the soil with nitrogen. To retain as compact a shape as possible in tree peonies, prune away shoots that have finished flowering, making cuts that remove most, but not all, of the new growth.