Eco-friendly Control of Botrytis and Phytophthora Blights on Peonies
Keep your peonies looking good and healthy with a bit of grooming.
Brown or purplish black spots on the leaves and stems of peonies are symptoms of Botrytis and Phytophthora blights. Both attack the leaves and stems though Botrytis can also infect flower buds causing them to turn brown and fail to open.
Several other fungal leaf and stem spots can cause similar damage. Symptoms range from small circular red spots to large irregular blotches on leaves, stems, and flowers.
These diseases are most common during wet and cloudy seasons.
Sanitation is usually enough to control these disease. Remove flowers as they fade and discolored infected flower buds as soon as they are found. Trim off and destroy infected stems and leaves. In fall do a thorough cleanup to reduce the source of infection next season.
Sanitation and a bit of cooperation from the weather are usually enough to keep these diseases under control.
A bit more information: Healthy peonies (hardy in zones 3 to 8) provide three seasons of interest. The foliage is a colorful red when it emerges in spring. The large, often fragrant, flowers add beauty to the spring garden and the foliage provides a green backdrop for other plants. As temperatures cool in fall the leaves turn a purplish red.