Are my peonies in trouble? - Ask Extension
My peonies have a white powdery substance on their leaves. What should I do about this?
Thank you!
Knowledgebase
Are my peonies in trouble? #871273
Asked June 03, 2024, 11:08 AM EDT
My peonies have a white powdery substance on their leaves. What should I do about this?
Thank you!
Howard County Maryland
Expert Response
Hi.
What you are seeing is powdery mildew, an extremely common fungus that appears on peonies and many other plants. While it is unslightly, the good news is that it is not likely to kill the plant.
Below is a link to an article from Colorado State University that will give you more information about the disease and the (fairly limited) treatment options.
Couple of other points: The appearance of powdery mildew can be very localized. I have a family member who has two stands of peonies no more than 60 feet apart from one another; one stand gets affected by mildew each year, the other is completely unaffected. The only difference between the stands is that the untroubled one gets a bit more sun. That, as well as less exposure to humidity, can make all the difference. This fall (don't do it now, it's too hot in the beginning of summer), consider relocating your peonies to a sunnier location with better air circulation.
If the mildew infestation is severe you could remove the affected leaves now. Otherwise, wait until the fall when the leaves die and fall to the ground. Pick up all the fallen leaf litter and trash it; this will help keep the fungus from surviving over the winter.
In addition, at the end of the growing season cut all your peonies down to the ground. This is true whether they are infected by mildew or not. (Disclaimer: don't do this if you have tree peonies, those with wooden stems, but from you photo it appears you have herbaceous peonies.)
I'm also attaching an informative article from an Extension Horticultural Assistant at the University of Nebraska.
http://extension.colostate.edu/topic-areas/yard-garden/powdery-mildews-2-902/
https://extension.unl.edu/statewide/buffalo/Yard/Peonies%20with%20Powdery%20Mildew%2010-15-2016.pdf
Bob
What you are seeing is powdery mildew, an extremely common fungus that appears on peonies and many other plants. While it is unslightly, the good news is that it is not likely to kill the plant.
Below is a link to an article from Colorado State University that will give you more information about the disease and the (fairly limited) treatment options.
Couple of other points: The appearance of powdery mildew can be very localized. I have a family member who has two stands of peonies no more than 60 feet apart from one another; one stand gets affected by mildew each year, the other is completely unaffected. The only difference between the stands is that the untroubled one gets a bit more sun. That, as well as less exposure to humidity, can make all the difference. This fall (don't do it now, it's too hot in the beginning of summer), consider relocating your peonies to a sunnier location with better air circulation.
If the mildew infestation is severe you could remove the affected leaves now. Otherwise, wait until the fall when the leaves die and fall to the ground. Pick up all the fallen leaf litter and trash it; this will help keep the fungus from surviving over the winter.
In addition, at the end of the growing season cut all your peonies down to the ground. This is true whether they are infected by mildew or not. (Disclaimer: don't do this if you have tree peonies, those with wooden stems, but from you photo it appears you have herbaceous peonies.)
I'm also attaching an informative article from an Extension Horticultural Assistant at the University of Nebraska.
http://extension.colostate.edu/topic-areas/yard-garden/powdery-mildews-2-902/
https://extension.unl.edu/statewide/buffalo/Yard/Peonies%20with%20Powdery%20Mildew%2010-15-2016.pdf
Bob
