When it comes to cutting peonies, many amateur gardeners are unsure. Here is what you can cut and what is better to leave.
Peonies are divided into herbaceous varieties and the so-called shrub peonies. These are not perennials, but ornamental shrubs with woody shoots. For several years there has also been a third group, the so-called intersectional hybrids. They are the result of crossing perennial peonies with shrub peonies and form shoots that are slightly woody only at the base. Because of these different growth characteristics, you will also have to proceed somewhat differently when pruning peonies, depending on the group of varieties.
Pruning perennial peonies
Pruning perennial peonies is basically no different than pruning other perennials. The herbaceous shoots die back above ground in winter and the plants sprout again in spring from the so-called overwintering buds, which are located on the tuber-like thickened roots.
Perennial peonies, like most herbaceous plants, are therefore cut back to ground level before new shoots appear in late winter. Order-loving amateur gardeners can also cut the perennials in the fall after the shoots have dried up, but it is better to prune in early spring, as the old leaves and shoots provide natural winter protection for the shoot buds near the surface.
Pruning shrub peonies
Unlike herbaceous peonies, shrub peonies are not pruned in the vast majority of cases. You can just let them grow, like many flowering shrubs, and they will grow larger and more magnificent over the years. However, there are two cases when you should reach for the scissors.
If the shrubs have only two bare basal shoots, pruning in the spring will stimulate branching. If necessary, quietly cut the branches back to the older wood. Even old branches will resprout in several places if site conditions are good. However, after severe pruning to 30 centimeters (12 in) above the ground, you will have to live with the fact that flowering will fail for at least one year.
The shoots of shrub peonies have rather brittle wood and therefore break off easily under larger snow loads. If the crown is still dense enough despite the damaged branch, you can simply cut the damaged branch below the break and above an bud sitting on the outside. If only two main branches remain after damage, or if the crown is suddenly very lopsided and irregular, it is recommended to prune all main shoots more severely in late winter.
In principle, shrub peonies sprout again without problems after rejuvenation into the old wood, but the shrubs must be vital and well established for this. Only then will they build up the necessary root pressure after pruning to be able to form new buds capable of budding on the old wood.
Pruning tips for intersectional hybrids
The so-called Itoh hybrids are treated much like perennial peonies as far as pruning is concerned. They are cut back to just above ground level, but the short woody stem bases are usually left in place. There are buds on some that will sprout new shoots in the spring. However, most of the new shoots form directly from the shoot buds on the roots, as in perennial peonies. In addition, some of the woody old shoot stubs die back in the spring, but this is not a big deal.