I correspond with the daughter of the original owners of my house (1962). She tells me her parents obtained the peony bulbs from a gardener at the Newport mansions and they arrived from England back in the day.

Anyways, I've lived here 2 years and they have gorgeous blooms, then not long after the blooms the leaves develop what appears to be powdery mildew (thanks Google!). I cut them back at the end of the season and the mildew recurred in the same way this year.

They are unsightly and I'd like to know if there is a way to prevent this. I can tell you there are a lot of them growing close together in a garden bed with a brick border. The soil is topped with large stones by the previous owner. I don't have supports for them. I try to obtain a couple at a time, but I can't afford to get enough for all the plants.

Thanks!

Some peonies are extremely susceptibles to powdery mildew (among mine Copper Kettle is always the worst affected) while others seem unaffected (MacKinac Grand). There's really not much you can do to prevent the disease: you can run the cleanest, tighest garden in the Western Hemisphere but if there are any powdery mildew spores in the neighborhood, they will find you.

The only thing you can do is being vigilant, and at the first sight of powdery mildew in your garden (there are even more susceptibles plants: when those show the first spots it's time to act) spray all susceptible plants with lime sulfur. It will stop powdery mildew dead in its tracks.
However know that powdery mildew will represent itself time and time again as lime sulfur gets washed away and new spores get released: it's just a matter of repeating the process. This year around here it was a veritable headache and I had to spray lime sulfur four times: thanks a lot to people who try growing pumpkins and squashes without ever spraying them "because chemical stuff is bad".
There are systemic fungicides which provide longer lasting protection but in my experience they are not as effective as lime sulfur is: the old (and dirt cheap) stuff is still unbeatable.

My experience is that shade in the morning tends to result in more powdery mildew problems. Also, peony stems seem to be more susceptible to it when they start to yellow and brown later in the season.

I also have more problems in areas where I plant too tightly and air flow is too poor to facilitate proper drying. Another way to get it going is for a lawn mower to blow wet grass into the peony. The grass carries it with it AND reduces air flow - sort of a one-two combo.

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Powdery mildew is common for some varieties here I think. The ones that are affected, I just simply cut back in August so I don't have to look at them anymore. In my experience in zone 5, spraying does me very little good and has not prevented, nor has good garden clean up, this from occurring the next year. I have neighboring plants to mildew susceptible ones, that are never affected. Personally, since I continue to enjoy the blooms when it flowers, I just accept it for what it is, to me anyway, a minor inconvenience.

In my garden, powdery mildew appears only on the peonies that are not underplanted; that is, if there is no groundcover around. If common violets (Viola sororia) (i.e., my main groundcover) grow around peonies, there is no powdery mildew.

@Jasmin interesting! Thanks for the suggestion. They don't have ground cover cause someone layered rocks at their bases.

Bria, I will pay more attention to powdery mildew next year and figure out which peonies are prone to the fungus. Hopefully, we will learn more about natural ways to deal with powdery mildew. In my case, only no maintenance solution is acceptable.

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The only peonies that get powdery mildew in my yard is Bowl of Beauty, I have 2 in different parts of the yard and both get it, never any surrounding plants. Like Tracey I cut them down in mid to late August.