Peonies are some of the most cheerful and stately plants to bloom in your spring perennial garden, with stunning blossoms and bold foliage. But have you noticed rusty spots on your peony leaves? If you have, don’t panic. You can prevent peony leaf rust.
Rust appears as small reddish or purple spots on the top of peony leaves and brown blotches on the underside. Over time, these small, circular marks grow into larger, more irregular blotches and may also appear on other parts of the plant.
Peony leaf rust, known as peony blotch, is caused by the fungal pathogen Cladosporium peaoniae, according to the Kemper Center for Home Gardening.
Peony blotch develops on peonies that lack adequate air circulation. Peony blotch fungus will also overwinter in affected leaf litter and old stems, attacking peony plants in the spring.
Rusty spots cannot be removed from the leaves. The only thing you can do is remove and throw away the affected parts of the plant. Do not put plant material that has rust on it into your compost pile.
The Iowa State University Department of Plant Pathology recommends that gardeners cut peony stems to the ground in fall or early spring and rake up all leaf and plant debris. Using fungicides may help when combined with the removal of diseased plant material and good air circulation.