There seems to be some correlation between pounding rain and peony blooming schedules. My two Japanese tree peonies were smacked down by heavy rain, but I did get to see their beautiful flowers for a fleeting day or so before the devastation. Now it’s time to assess their structure, which is a bit wonky from abusive weather. I suspect they don’t stand up well to the weight of snow accumulating in their interior structure, causing the woody stems to splay open. Fortunately, pruning is a good way to rejuvenate them.
I should point out that it’s better to prune tree peonies in early spring, when their pink buds are prominent, but not yet open. But truth be known, I’ve never done this work on time, and always get to it after the flowers are just finished, usually in early June.
Their branches live for about four years, and are replaced by new wood that sprouts every year. This natural renewal process saves quite a bit of anxiety when it comes to pruning. It’s only necessary to cut out obviously dead wood, either entire branches (cut back to the crown), or upper sections and side twigs of living branches (remove only the dead sections), cutting to just above a living bud. The end result should leave every branch with a living bud at the top. (Herbaceous peonies behave differently: their stems die back to the ground each winter and the plant sprouts new growth in the spring.)
But my tree peonies have living wood splayed open, with some branches in an almost horizontal position. As buds sprout, the weight of upward-facing new growth has no proper support and falls sideways. Flowers end up on the ground and it’s a mess! What I’ve learned is that Japanese peonies have many buds along their branches, both those that are visible and other adventitious buds hidden in the thin bark. The plants are quite responsive to pruning, and will activate their buds when living sections are removed. I just do what’s necessary, and remove any branches that aren’t sufficiently perpendicular, shaping the plant into an open form with branches leaning slightly outward and pointing upward. Taking off living wood means I’m losing some of next year’s flower buds, but the plant is quick to open buds and make new shoots.
My tree peonies got into such a mess because I was afraid to prune them. Now I see that it’s easily done, and the plants are quick to come back with new growth. So take courage and just do it.