Experts and BHG readers answer.
Mildew on Peonies
I have dozens of heirloom peonies that have, for the first time ever, been devastated by powdery mildew. What should I do to help these dowager queens recover and not suffer reinfection next year? They are on well drained soil and mulched with wood chips. They usually are very self sufficient. HELP!
Hi! Thanks for writing. Most peonies are susceptible to powdery mildew when the weather is right for the disease. Happily, in most cases, the powdery mildew won't harm your peonies, just make them look bad. If it looks like it's going to be a bad year for powdery mildew, you can spray your plants with a fungicide as a preventive treatment. But it's only really effective if you spray before the disease takes hold.
Ensuring your plants get plenty of airflow, aren't fertilized excessively, and don't get overhead watering (such as from a sprinkler) can also help prevent infection. Learn more! http://www.bhg.com/gardening/pests/insects-diseases-weeds/stop-powdery-mildew/ ---Justin, Senior Garden Editor, BHG.com