Spots On Hydrangea Leaves - Knowledgebase Question

Austin, TX
Question by benavih
June 7, 1998
I planted a beautiful hydrangea plant this spring in a large pot. Initially placed where it received some morning sun, the leaves looked wilted. I then moved the plant to the shade where it gets some filtered light in the afternoon. Although it has bloomed nicely so far, some of the older deep green leaves have faded white spots on them. The newer leaves don't have this. Is this a result of not enough sun? Could it be that the leaves turn limp in the sun because it is in a pot rather than in the ground?


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Answer from NGA
June 7, 1998

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The spots you described could be caused by powdery mildew or sunburn. Although you've seen hydrangeas in more sun, when a plant grows accustomed to a given light level, moving it to a brighter location can cause temporary problems. It may be the spots came from initial damage when it was in the brighter location. Sunburn should show up primarily between veins of the leaf and appear as dry pale leaf tissue. If this is the cause, the plant will soon adjust and recover.

Powdery mildew looks like a very fine powder in somewhat circular patches on the surface of the leaf. Often these spots are bordered by yellow "halo's". Products with neem oil are an organic option to keep powdery mildew in check. An organic home remedy some people use is a spray mix of 1 tablespoon of baking soda in 1 quart of water.

Wilting is a common problem of hydrangeas in somewhat sunny locations. They need a moist soil, but even with adequate moisture, the roots often can't keep up with the amount of water the leaves will transpire when the sun shines on them. Container plants are all the more susceptible as their root system is restricted. You may need to water twice a day to keep up!

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