Question:
What is wrong with my peony leaves?Answer:
Foliar diseases like leaf blotch and powdery mildew can discolor or spot peony leaves. Peony leaf blotch (Cladosporium) causes irregular brownish-purple spots on peony leaves in summer. The powdery mildew fungus (Erysiphe) covers the leaves in what looks like a dusting of white powder. See photo below. Once these diseases appear on the leaves, there is little that a gardener can do. Fortunately, both types of foliar diseases do not typically kill peony plants. In the fall remove the diseased leaves and discard them to prevent re-infection next year. Diseased leaves should not be composted.
Another consideration may be the location of the peonies. Peonies planted in too much shade frequently have more problems with foliar diseases than peonies in full sun.
Learn more about growing peonies in Iowa in this article: Growing Peonies in Iowa
