Hydrangea leaves are turning brown

Asked September 8, 2020, 9:47 PM EDT

My hydrangea is very full and bushy and produces plenty of flowers. But I've recently noticed that the leaves have developed extensive brown spots. I've attached 2 photos. The plant gets full sun in the morning and is shaded in the afternoon. I'm hoping you can tell me what is causing the brown leaves and what I might do to restore the health of my plant. Thank you.

Montgomery County Maryland

1 Response

This year many hydrangeas developed reddish-brown or purple leaf spots – symptoms of bacterial leaf spot caused by Xanthomonas campestris. This disease commonly occurs during warm, wet weather in late spring and early summer. While hydrangea species, such as H. arborescens and H. macrophylla, are susceptible, the disease seems to be most severe on oakleaf hydrangeas.

Symptoms are usually first observed on lower leaves, and the pathogen moves upward in the plant canopy through rainsplash or overhead irrigation. In the landscape, you can remove lower leaves as soon as leaf spots are first observed to help slow disease spread. Overhead irrigation of hydrangeas should be avoided. Always water at the base of the plant. Increased plant spacing or pruning back plants that crowd the hydrangea can help increase air circulation, keeping foliage as dry as possible reduce disease. The amount of these leaf spots varies from year to year. It is cosmetic, and no treatment is necessary.