Question
What can I do about brown spots on my two Hydranga plants? One plant is a year old. The other plant is at least seven years old.

The small spots are in various places on some leaves. The large spots are on the edges of some leaves.

I look forward to your answer.
Thank you

Answer
There are two main leaf spots that affect hydrangea.  They both cause brown spots, so you will have to do a little investigation yourself to figure it out.  

The first is Cercospora leaf spot and it causes many small spots.  The spots may eventually coalesce so that large areas are affected.  The second problem is anthracnose.  This disease has larger spots which are sometimes target shaped.  

I suggest you visit the following website because it provides both images of the spots as well as information about the diseases.  http://www.aces.edu/pubs/docs/A/ANR-1212/ANR-1212.pdf

Good luck!