White Mold on Peonies: Fall Sanitation Is the Cure

White powdery coating on peony stems and leaves is powdery mildew, a common late-season fungus. It rarely kills the plant but weakens it.

Fall Cleanup Protocol

1. After frost, cut all stems to ground level.
2. Remove every piece of debris—bag and trash, don't compost.
3. Apply a fresh 2″ mulch layer.

Spring Prevention

• Space plants for air flow.
• Water at base only.
• Apply preventive sulfur or neem oil at bud break.

Resource

University of Minnesota Extension has a detailed guide (search "peony powdery mildew DG1153").

Sanitation breaks the cycle. Next year's foliage will be clean.