Pruning peonies applies to the tree peony, since their established plants are woody shrubs that will benefit from pruning. Young tree peonies shouldn't be pruned for the first couple of years. It's only necessary to remove dead wood or possibly a broken branch while they're getting started. If their shape is pleasing after that, little if any pruning is needed.

Remember that tree peonies are not herbaceous. They do not die down to the ground every year after their season is over. They grow very slowly but eventually reach 4 or 5 or even 7 feet in height and do not need staking.

Natural branching will occur with Chinese and American types of tree peony as they grow. At times, an entire branch may die, however. In this case, pruning peonies involves checking the shrubs in February and cutting any dead branch back until you see a live bud. Otherwise, do not cut them back unless they are seriously misshapen. Japanese and French types of tree peony grow somewhat differently and may need more regular pruning.

Additional Hints for Pruning Peonies

Pruning peonies should normally be done in the spring. It may have an effect on the number of flowers you see this season, but will be worth it. Nothing horrible will happen if you prune after the flowers have finished blooming, but the tree will recover more slowly, and it's a slow grower to begin with. Occasionally you will come across an older tree that has never been pruned. Trim only one branch back each year, so as not to shock the plant. But cut it way back if needed, again till you see a live bud.