Spots on Hydrangea Leaves

Spots on Hydrangea Leaves

“I have spots on my hydrangea leaves,” the customer said. “I’ll send you a picture by email because I’m afraid it’s dying. Maybe it came from a bad batch.” We suspected that the “batch” of hydrangeas was just fine, and that the plant would recover very nicely, and once the photo arrived this hunch was confirmed. The hydrangea just has a leaf spot fungus, something that this type of plant is prone to in certain situations.

Hydrangeas get leaf spot when their foliage is frequently hit with water. Sometimes it begins in cool, wet spring weather. (Typical for May and even June on Cape Cod!) Other times irrigation systems are to blame; although hydrangeas like soil that is well-drained but moist, a sprinkler that hits the leaves every other day, or even every three days, will produce leaf spot.

People will commonly see leaf spot on newly planted hydrangeas. This is because most garden centers that stock these plants have no choice but to use over-head irrigation that comes on every morning before the nursery opens. After a few weeks of this the plant will already have leaf spot brewing and this often shows up when the plant has already been placed in a customer’s garden.

Here’s the good news: the leaf spot on Hydrangeas is usually a cosmetic problem only. It doesn’t kill the plants. Once the watering methods have changed the plant will no longer get new spots on the foliage. If there are some leaves that are particularly ugly those can be clipped off to improve the appearance of the plant. As long as the Hydrangea isn’t getting hit frequently with overhead watering in the future the problem won’t reoccur…unless, of course, the weather is especially unfavorable.

Although treatment for this leaf spot isn’t usually needed, if you want to apply an organic fungicide to protect unmarked foliage in the future, Actinovate, Serenade, or similar products are a good choice.

If you have no choice but to water with over-head irrigation, be sure to water deeply less often. You're less likely to get leaf spot if you water every four or five days for a longer period of time instead of every other day for twenty minutes.

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