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Powdery mildew - impact on other plants #812371

Asked September 27, 2022, 10:53 AM EDT

Hello! I have five peony plants that I planted in a mostly shaded part of a landscape bed two years ago. For the past year, the plants have struggled with powdery mildew. I am considering moving the affected plants to a different landscape bed that will get full sun. Based on what I've read, once a plant has powdery mildew problems, it cannot be cured. My question: does moving the affected plants put everything in my new sunny plant bed at risk for getting powdery mildew? In other words, I'm debating the risk / reward - by moving these peonies, is there a chance that they will perform better and be less susceptible to powdery mildew in future years AND what risk does making that move pose to my plants in the new location (currently planted with bearded iris, coneflowers, and aster). As a build on to the question, if I do move the peonies, do I need to take any special care to the soil in the old bed (where the peonies are taken from) to ensure anything I plant in that place is not impacted? Thank you very much for sharing your perspective and expertise! Andrea

Ramsey County Minnesota

Expert Response

Hi Andrea,

Powdery mildew is a fleeting summer problem and does not linger in the tissue of your peonies. The plants prefer sun and should do better in the new location. Make sure to give them enough space so air circulation is good, which will reduce the chances of a reoccurrence.

Cut the plants down to the ground before transplanting and rake up and bag all the mildewed foliage to get it out of your yard. Sanitation is a key to reducing the possibility of mildew next year. Every fall, you should cut peony stems down to reduce the chance of disease.

That said, sometimes there’s lots of powdery mildew around. This is one of those years. And some peonies are susceptible to mildew. A few years ago I had a badly infected peony turn totally brown with mildew while inches away another peony was never infected. That severely infected plant has been fine since.

Here’s info on powdery mildew on peonies: 

https://extension.unl.edu/statewide/buffalo/Yard/Peonies%20with%20Powdery%20Mildew%2010-15-2016.pdf

Now is a good time to move your peonies. If you haven’t done it before, planting depth is key. The pink buds (called “eyes”) at the crown of the plant are next year’s growth shoots. They should be planted one to two inches below soil level and no deeper or they will not flower. It’s easier to move the peonies if you shake the dirt off the roots.

Sometimes after being moved peonies don’t flower for a year. But if planted properly they should rebound. If you move them now, and this is the best time to do so, water well and mulch them with leaves or wood chips to provide some winter protection for this first year.

Here’s more info on moving peonies:

 https://extension.unl.edu/statewide/buffalo/Yard/Peonies%20with%20Powdery%20Mildew%2010-15-2016.pdf

Lots of plants are susceptible to powdery mildew but moving the peonies to the new bed will not spread it there. Just make sure the peonies have enough room. 

Good luck.

MJ Replied September 28, 2022, 12:24 PM EDT

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