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Fort Worth, TX
Bcrowell
Jun 2, 2020 7:26 PM CST
I have three, four month old oak leaf hydrangea's that are now showing small dark spots on the leaves. How should I treat?
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Name: one-eye-luke US.Vet.
Texas (Zone 8a)
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oneeyeluke
Jun 3, 2020 2:18 AM CST
Its from too much water and probably happened a few weeks or even a month ago. If your were getting too much water now, the top leaves would be showing edema, but since its below on the lower leaves, I would say maybe a few weeks or a month ago your Hydrangea got too much water. Let the soil dry well and keep the top couple inches of soil loose and cultivated.
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Name: Lynda Horn
Arkansas (Zone 7b)
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gardenfish
Jun 3, 2020 3:02 AM CST
That is not caused by too much water. Appears to be a leaf spot disease.
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Name: Luis
Hurst, TX, U.S.A. (Zone 8a)
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luis_pr
Jun 3, 2020 9:04 AM CST
At this point, the leaf damage resembles that caused by a form of leaf spot. But the typical leaf spot in this area is cercospora leaf spot, which makes the spots develop a bit of a halo and this halo is not present in the picture. Strange. It is also quite early to be seeing this problem as it tends to appear closer to the end of the growing season, not in June.

If the leaves are getting wet, please modify hand watering such that you water the soil but never the leaves. If you are using a sprinkler, water closer to sunrise so the leaves dry out quickly and do not remain wet overnight for long periods. If the plants already had this problem due to overhead watering at the plant nursery, well, nothing we can do but use clean sanitation practices to make things difficult for the leaf spot fungi. This includes quickly picking up any plant debris (leaves, flower, dead wood) and throwing it away in the trash, not in a compost pile. In the Fall, all of these will brown out and some will fall down during winter. You can deadhead leftover blooms in early Spring but just cut the peduncle, the little string that connects the bloom to the hydrangea stem or branches (do not cut the stem/branches as invisible flower buds from the summer will be hiding inside the ends of the branches or stems). The flower buds will open in March or so provided you do not cut/prune the ends of the stems/branches where they are hidden. Do not let the foliage get wet but do as much as you can practically do. Do not overwater such that the environment around the plant is way too humid, which fungi prefer. Improve air flow around the plant by not letting other plants contact the hydrangea leaves. Increasing the amount of sunlight around them in any way can also help make things uncomfortable for the fungi. You can raise the canopy of trees or other plants for that purpose, etc.

Also do really watch out for overwatering. We have gotten a lot of water this season. When that happens, it is not necessary to hand water or use the sprinkler if Mother Nature has already done the work for us. But even a more concern, you could be promoting root rot. So if we get about 1" or more, you can probably skip watering although that depends one one's soil type, etc. Just a thought.

Oakleaf hydrangeas are notorious for getting root rot when the roots are in wet soil for 'too long'. I lost an Alice Oakleaf Hydrangea some years ago when we had a lot of rain in Spring and part of the Summer so, I always tell folks to make sure the soil drains well so they do not stand in wet soil for too long of a time. All hydrangeas can suffer from root rot but oakleaf hydrangeas catch it more easily. They are quite drought tolerant once they become established in the garden so they are good choice in my old stumping grounds of west Fort Worth.

Where did you purchase these guys and what kind are they? I used to get them at Archie's Gardenland at one time but the bbig stores now include them some times. Alice gets quite large for many areas so I would recommend more compact versions. You can see several good Alice Hydrangea specimens at the Grapevine Botanical Gardens in Heritage Park in Grapevine, near the intersection of William D. Tate Avenue and TX-114 in NE Tarrant County. Not too many people visiting nowadays so it feels safe but take your mask in case it happens to be busier when you show up. Turn north on William D. Tate Avenue. The avenue changes name to Ball Street and, after 3 blocks or so, it will be on your right after a church.

[Last edited by luis_pr - Jun 3, 2020 9:36 AM (+)]
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