What are the dark spots on the leaves of my hydrangea?

Black spot fungus is usually caused by overhead watering. For healthy foliage, water at the base of the plant. Black spot can also be a sign of poor air circulation or caused by rainy, humid nights. When these leaves drop off, be certain to gather them up and throw them away. Don’t compost them. If you are overhead watering, just adjust that practice next year and it won’t be a problem. The Endless Summer Hydrangea planting and care guide has additional tips for growing healthy plants.