Hydrangea problems: is this a disease or fungus?
There has been a lot of leaf spotting on hydrangeas this year, primarily due to the wet spring/early summer. Even on hydrangeas that have never previously had spotting.
It could be a fungal or bacterial leaf spot. It is not systemic in the plant, only on the leaves.. All the leaves will fall soon. Leaves can be disposed of in the trash, but do not have to be. If the site is overly shady, trying pruning back adjacent plants to improve air circulation.