Plant Diseases/Blotches on Oakleaf Hydrangea Leaves
Hello Dr. Vann. Thank you for answering my question. My name is Tim Elliott, and I live in Kingman, KS (zone 6b). Attached are three links to photos of my recently planted Snow Queen Oakleaf Hydrangea plants. There seems to be some sort of large brown blotches forming on the upper leaves. They were very healthy when I planted them, and they still seem very healthy, since they are not wilting. I couldnít see any sign of insect infestation, such as spider mites, on the tops or bottoms of the leaves.
They are planted on the north side of my house in sandy loam with a little bit of clay. The soil is very well-drained and the plants only receive about 1.5 hours of early morning sun and approximately 2 hours of late afternoon sun. I also have them mulched with 3-4Ē of pine needles. We have had a lot of rain so far this summer and as a result many days of overcast skies. I wasnít sure if the moisture and cloudy days had something to do with the blotches?
The three links below include two photos of plants with the blotches and one that doesnít have any blotches at all. Interesting enough the Snow Queen Hydrangea plant without the blotches is planted right in between the two that have the blotches. I also have two Ruby Slippers Hydrangeas, (one on the east side of my house and one on the northeast side of my house), that have no blotches either.
Would you be able to tell me what these blotches are and what is causing them? Iím guessing itís a combination of recently transplanted, unestablished plants, and the wet, overcast environmental that will clear up when the weather does, but I wanted an expert opinion to make sure. But if it is fungal or viral, how do I treat it and why is the plant in the middle not affected?
Finally, if it is environmental and the weather does not clear up before the plants enter dormancy in the Fall, do you think they will survive the winter?
Please let me know what you think these blotches are and how I treat them or if I even need to.
Photo of first plant with blotches:
Photo of second plant with blotches:
Photo of plant without blotches planted in between two other plants with blotches:
I do not recognize these leaf symptoms associated with an infectious problem (disease or insect). From your photo, the blotches seem a bit uniform and located mostly in the same part of the leaf. Based on this, I would be suspicious of an environmental issue as you mentioned rather than the infectious issue. Follow the new foliage forming for changes.
Identifying the environmental stress can be tricky- it may even be a combination. In order to rule out a nutritional source, you may wish to have a soil test done. You can contact your local County Agricultural Extension Service and arrange to have a soil test done. Usually very inexpensive as well! The office is usually in the courthouse of each county. There is an Extension component to the Land Grant University there in Kansas too.