I have two peony plants in my lawn: The image above is of my peony located in the front lawn. It sits in shade most of the day and has MANY plant companions planted around it. Every year it gets powdery mildew while my peony planted in the back yard (full sun, very few plants around) has never had a problem with powdery mildew.
So lets explore this. First, you should know that I am possibly the worst person when it comes to landscaping. I tend to just plant all my plants in this one corner of my front lawn because I don’t know what else to do with them. I thought they would look fabulous there, but as the plants continue to mature and expand in growth, they look less fab and more crowded then anything. So, we have little air circulation. That’s problem number 1. The next issue is the amount of shade this particular peony receives – Powdery Mildew tends to thrive on plants that: 1.) sit in shade, 2.) have little air circulation, 3.) During times of high humidity. Check, check, and check. This peony meets all of the ideal environmental circumstances for powdery mildew to develop.
Powdery Mildew is more of a cosmetic issue, very seldom will it do long term damage to the plant (in fact, I have a lilac bush in the back yard corner that gets it every year too). To correct it, I have a couple of options available. I can dig up and replant the peonies in a better location where they will get more sun and air circulation, I could also schedule a preventative fungicide for next spring, or I can just leave it be knowing that although it’s unsightly, it’s not going to kill my plant.
You will also note some leaf spot on the leaves. I will continue to monitor those to see what they do, I’m hoping it’s just from all the rain we had earlier this year and there is nothing to really worry about.