Do not know why I can not upload more than one pic in my first post. Anyway, do you know what is on my peony leaves? Is it harmful? Do I need to do anything? Thank you very much

It is Powdery mildew. Cut the foliage and dispose of in the trash. It is generally thought that a combination of high humidity and dry soil triggers it. Good air circulation around the plant can help. Is it growing in full sun?

This type of mildew has only been around for a few years. Some peonies are more susceptible than others. It does not seem to make any difference in how the plants are grown. I have seen it in full sun on a plant separate from others and in a mass planting where only one or two of the plants are completely covered. While I agree with removing the foliage I do not. Last year I had many plants with it this year only a cluster of five has it on the foliage. They are isolated from the rest so will be leaving them as an experiment to see what happens. I also have one plant that has the mildew on three of the seed pods but not on the rest.

In my opinion, most PM is omnipresent, and afflicts plants that are stressed (like drought stress in particular).

Its August - peonies look crummy in August. You worry, you despair, you cut 'em down and... they grow back fine the next spring.

I agree with Ken, though I suspect unless conditions/culture changes, PM will ever be with you. Still, good practices are worth doing.

I would also keep the leaves because they are still working, and we have a lot of time left in the growing season. I use the "Cornell formula" to clean the powdery residue. It works to some degree -- the leaves will be clear of the mildew but they will never look nice and smooth again, and there may be some discoloration. Don't spray in hot weather when the sun is out.

Cornell formula: 1 gal water, 1 tablespoon baking soda, 1 tablespoon horticultural oil. Some folks also add liquid dish soap, but it's not needed if you are using horticultural oil (it includes a sticker-spreader). I use Bonide all-season oil.

As other posters mentioned, plants are susceptible to powdery mildew when the soil dries out but the air stays humid. Regular watering helps keep it under control.

Even at the small amount of horticultural oil do not spray on the leaves when the sun is shining on them. May cause burn spots on the leaves as the oil can magnify the light.

Side q. I know the water drops on the leaves causing magnification burn was debunked as an old wives tail... should the same be said of oil ? I can’t see it causing enough magnification to do anything

Thank you all for the replies. Yes, this summer is very dry and I did not supplement water. They should have good air circulation though unless their leaves are too dense? I guess I will do nothing then. Again thanks

Nevermore, highly refined, all season horticultural oil (not the heavy dormant season stuff) is not known to cause a phytotoxic reaction. Although neem oil (a plant/vegetable based oil) has been noted to cause some reactions on certain plants or plant types. And the reaction has nothing to do with magnification :-) It is just a chemical reaction involving the sprays, sunlight and plant tissue. Some plants are just very sensitive....others not at all.

I have same problem w my peony. Also I have buds that never opened. ?? I had three gorgeous blooms then nothing. As far as cutting branches to open it up for circulation, how “open “ should it be? Don’t wanna make it skimpy. But cutting now would make a difference in spring? As far as circulation? I would love more blooms next year. TIA

Powdery mildew and unopened buds are two different issues. If you have the PM, cut back your peonies now and dispose of all the foliage. Cutting off the foliage at this time of year has no effect on the plant for next season or how many flowers it might produce.

There are various reasons for lack of flowering but unopened buds are usually due to insufficient sunlight or an early season fungal issue.....like botrytis. PM is a late season problem.

Some years if the buds are larger non-opening can be caused by the weather. When the temperatures turn from mid 70's to mid to upper 90's with low humidity the covering will shrink and not allow the bloom to open. When this happens if the bud is far enough advanced to show color the petals will appear dry.

You might want to try a fertilizer with a higher middle number than 1st, skiier. I never fertilized my peonies, not really necessary, but tried after seeing how many more 1st year blooms some of my forum friends got than I did---makes a lot of difference. FlowerTone by Epsoma is what I use, BulbTone is good as well, but any organic fertilizer with that higher middle number should do the trick. Look for one with potash to help with flowering.

I have the issue maifleur describes every year on my latest bloomers and I'm a zone 4b, just goes to show it can happen in the cooler zones as well.

I have 160. I’m a micro climate property with a wet land. I have peonies in areas 4a,4b and 5. In all types of soil. This is my cooler ground. I live in Syracuse NY area. I have all of the issues. Yes, everyone is correct. Some plants are just more inclined to it. The buds not opening for me is a wet rainy year on some. B gets us all. I stopped worrying about it. I do find , however, cutting back too early lessens the whole plant on many. We were very dry and then wet this year. I had 4 plans with pm on the Lower stems only. If you are inclined to do so, I have used the chemical Daconsil(spelling). It does work but, I thought better of the chemicals. I used it once it does work. I prefer natural rather than chemicals. I just don’t worry Any longer. Always cut and burn or bag and remove. The weather really is the key and you don’t control the weather. Mine always show well if left. I do cut b if the plant gets to much. Clean your clippers as you go to prevent passing it to more plants.