Treating Powdery Mildew on Peonies
After many years of beautiful, trouble-free peonies, they are suddenly covered with powdery mildew, especially the stems. This year, there is probably nothing I can do, since the whole row (about 50 feet) is affected, but I need advice to save them for the future:
1. Should I cut back the affected stems now or wait until fall?
2. Should I treat the remaining plants and stubble with fungicide as well?
3. They look crowded. Do they need to be thinned?
4. The neighbor has new trees and bushes which reduce the light, so I suspect that to be part of the problem. Would they need to be altogether transplanted?
I HOPE TO AVOID SOLUTIONS 3 AND 4!
Thank you very much.
Certified GKH Gardening Expert
Yes, you can remove affected growth. You can actually cut the entire plant to the ground in fall if desired. These articles will help with the powdery mildew: https://www.gardeningknowhow.com/problems/get-the-cure-for-powdery-mildew.htm
Peonies are very finicky when replanted. It may take them a year or two before they recover from transplant shock, so take this into consideration before moving them. Your neighbor may be willing to trim back the trees/bushes some if asked nicely. :) If you need help with dividing plants to ease overcrowding, here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/flowers/peony/dividing-peony-plants.htm
You can also spray the entire plant down with a product called Green Cure. It is available on-line and at some garden centers locally. It is one of the very best I have found at getting rid of powdery mildew problems.