Hydrangea Rust?

Question: Not sure what this is all over my Hydrangea serrata 'Tuff Stuff Aha'. Is it rust?

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 14, 2023, 12:12 PM EDT
response: Hi,  To our knowledge, Hydrangea serrata don't get rust symptoms. Missouri Botanical Gardens has a plant profile page about them that you can review. They can be susceptible to fungal leaf spots which is often caused from excessive rain (we haven't had that) or overhead watering, but these symptoms don't look like that. It could possibly be from the drought conditions we are experiencing, they do like evenly moist soil conditions, especially if they receive more mid or late day stronger sun (although we suspect the leaf tips would be turning more brown and 'crispy' if they were dry). What is your watering schedule for these?  Or it could be the beginning signs of powdery mildew. Despite our dry conditions, powdery mildew is still showing up on landscape plants.  There isn't a treatment that you can do or is warranted right now, just monitor the symptoms and let us know if the plant seems to be failing drastically. When supplementing watering needs, make sure to water at the base of the plant and try to avoid getting the leaves wet or splashing water on them. This can help curb any leaf spot or fungal diseases. With our generally humid Mid-Atlantic weather, fungus is just a part of life unfortunately, but most of the time it just causes a somewhat unsightly appearance and not devastating health effects to the plant.  Please feel free to reach back out if there are worsening symptoms or decline. Emily

responder: The Question Asker Replied June 14, 2023, 5:05 PM EDT
response: Hi Emily,    This Hydrangea serrata is by itself and there are 3 others 10 feet away doing just fine. You are probably correct about the watering. Since they haven't drooped at all, I haven't been watering. The foliage looks perky in dappled dry shade all day. No direct sunlight, as are the other 3. And all 4 are beginning to flower. I will start watering the ground (not the plants) twice a week deeply if we aren't getting a soaking rain. If you don't think it's a fugal issue, I won't spray with a copper fungicide.    Thank you!   Bell

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 15, 2023, 9:51 AM EDT
response: Hello Bell,  Even if this is a fungal issue, we discourage the use of fungicide if it's not needed to save a plant from drastic damage (not the case for hydrangea infections) as these products might risk harm to pollinators or other organisms, plus fungicides don't always work perfectly well to prevent infection. Copper also remains in the soil so there is a limit to how many applications can be made per year, and since such diseases tend to be recurring as they are naturally-occurring, we'd like to reduce the risk of harmful soil buildup. Any badly-infected individual leaves that might manifest later in the season can be snipped off, and all shed or frost-killed foliage can be removed at the end of the season in late fall, but otherwise nothing special usually needs to be done about leaf infections that hydrangeas can contract.  Miri

responder: The Question Asker Replied June 15, 2023, 5:05 PM EDT
response: Thank you so much! Ive been hearing more and more about the downsides of fungicide. I will pass this information on to others also.

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 15, 2023, 5:32 PM EDT
response: You're welcome!