For the last 3 years, my peonies have developed a fine white dust on the lower leaves which I have treated organically. I have now removed the peonies, which no longer bloom. Should I treat the soil in any way prior to planting to prevent recurrence of the fungus in the new plants? Thank you in advance for your advice.
Kent County Michigan
You are probably noticing Powdery Mildew, which is both common and mainly aesthetic. Here is a great cultural sheet to help with your peony care and another one about powdery mildew.