The damage is already in the leaves. Some of the black spots are fungus but there can be other causes like a bug bite or something hitting the leaf and stem, hail, blown objects. Cutting back will not do anything either way for the flowers unless you leave the cut portion in the area of the plants. If it is fungus the spoors could infect the plant. I personally do not worry about the black spots because many peonies will have them when we have wetter than normal seasons.

By now the plant is starting to go dormant so you can cut if you wish or leave until frost. But do remove the cut portion.

Thanks very much!

Hello and thanks. I'm new at peonies and also have the same problem. How far should I cut them back? Should I cut them to the ground every year? Joyce

Since I have several that display wonderful autumn colors I wait until after the first hard freeze before cutting. Most years there will be some damage from various things which causes most of the black spots. When I do cut down I leave about 3-4 inches above the ground so I will know where the plant when I add things like fall planted bulbs or annuals next spring.

Although you do need the leaves for photosynthesis, it's better to cut the leaves off the affected leaves now. Cut it to within 1-2" from the ground. You want to stop the disease from getting down to the root system.

I agree with the others on the UNAFFECTED LEAVES. Part of the beauty of peonies is that the foliage contribute color to the fall landscape.

Cutting the leaves off as mentioned in the first paragraph is an annual event in the maintainance of the peony plant which I normally do at the end of September. Easier to keep track of it. Please make sure that all the cut leaves and stems go straight to the trash and not any compost piles (which means off the peony plant bed too). You don't want any overwintering of any virus diseases to occur.

Only cut back the stems of the herbaceous types of peonies. Those that do not develop woody stems. Do NOT cut back tree peonies.