it sounds like Cercospora leaf spot. Here is a link for diseases hydrangeas get. Check with your local nursery for leaf spot fungicied. Here is a link that might be useful: Hydrangea diseases

Probably a fungus like leaf spot. I've never done it, but you could probably treat it with a fungicide if it really, really bothers you. I see it lots. It seems to me to be a good barometer of the stress that the plant is going through. For me, if the plant is not stressed I see very little of it. And so if I see it, I try to find the source of the stress. Being in the ground for only a month is pretty stressful for a plant. Good Luck. Hay.

Hello, Annie. A picture would be very useful in this case since now is a time when many hydrangeas develop fungal diseases. Leaf spot is the most common and, at times, looks like brown spots. Most people take no action this late in the year because the plant is about to go dormant and the leaves will dry off. At that point, you can just throw the leaves in the trash (not the compost bin). Hydrangea blooms change color many times throughout the year, specially in the fall. Many colored varieties will be turning brown this time of the year so, if yours is doing this, it may be doing that simply because it is "that time of the year". That is not to say that this is THE reason though. Premature change of color towards brown can also indicate that the plant is not getting getting enough water. Since you are concerned about watering issues, manually check it. On a daily basis, insert a finger into the soil to a depth of 4" and see how the soil feels. If it feels dry or almost dry then water. If it feels moist, do nothing. If it feels wet, try to see why since the soil should not be wet unless it has recently rained or something like that. After a while, you should notice that you are watering on a certain schedule (every two/three/etc days) so set your sprinkler to water on that frequency. As the temperatures change (10-15 degrees) and stay there, you may want to manually recheck. By the time your plant goes dormant, you can reduce watering to once a week or once every two weeks. Remember to water during dry winters too. Jfraga, what variety of hydrangea do you have? Browned leaves that start brown in the edges indicates lack of moisture so check your plant as I described for Annie and water it. If you have a small (new) shrub, you can start with 1g of water every time you water. Does that help you guys? Luis

It is probably from too much sun and lack of moisture during the hottest part of the day. I sadly forgot to water during the recent heat we have had and my white strawberry vanillas turned to light pink to brown quickly. I planted them this spring and they needed water faster than I anticipated I noticed they were wilting before I watered so the mature blooms aren't going to look good this year, although the plants are thriving. It is unfortunate. I planted 4 at the north end of my property and they get all day sun. I will gave to evaluate how they handle the sun next summer because I do not want to move them but I also do not wan their beauty wasted.