Mildew on peony leaves

(Question)

My peony leaves got mildew on them and treatment didn’t work. This plant is in a winterized pot and new to me this year. Should I cut off all the leaves and throw them out to reduce chances of the same thing happening next year? (My peony in the garden did not get mildew. The affected one is in a hot, dry location on the deck). I’m in Scarborough.
Thank you for your assistance.

(Answer)

Powdery mildew thrives on some peonies more than others and in hot, humid weather. Treatment with sprays works better for prevention than treatment. You should cut off all the mildewed leaves and dispose of them in the city compost rather than your own compost pile, if you have one. This can be done now. Powdery mildew looks unattractive, but doesn’t affect the long term health of peonies, so I wouldn’t worry about it too much. I’m not sure if it makes any difference that your peony with mildew was in a pot, however some cultivars are more resistant than others.

Following is a link to an answer previously given on the Toronto Master Gardener website about powdery mildew on peonies.

https://www.torontomastergardeners.ca/askagardener/white-powder-pla…erennials-threat/