Dear Brian,

Thank you for contacting us about your hydrangea. When leaves change color in the summer, it is usually a sign of either root damage or  environmental stress such as depleted soil nutrients, over- or under-watering, poor planting, and temperature (high or low).

How long has this been an issue for this particular plant? Has anything changed around the plant since last year? Is it possible that something was added to the soil, or that an herbicide was used nearby? The blooms appear stunted. Is that the case?

To know what is going on we have to consider a wide range of possible causes. If you have any more information, please send it as a reply to this email. 

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Hello Brian,

Thank you for the additional information. There are no pests that might cause this reaction in your hydrangea so I am thinking this must be an abiotic (environmental) issue. There are a couple of possibilities.

There may be a drainage issue that has arisen due to the particular site nearest your house. I suggest you check the soil moisture before irrigating. Push your finger into the soil about halfway. If the soil feels cool and damp, wait another day to check again. Water the plant when the soil feel dry about 2 inches deep. (btw - lawn sprinklers do not provide sufficient moisture for trees and shrubs. Use a soaker hose or drip irrigation system so the water will slowly soak into the soil to a 2-inch depth.)

The site may also create a microclimate for this particular plant. We had extreme cold this past winter, and extreme heat this summer. Either could stress the plant sufficiently to cause a reaction. 

I suggest you maintain about 3 inches of mulch across the root zone, and water when needed as I mentioned above. Keep an eye on the plant in case any portion begins to show signs of dieback, but the shrub may just recover on it's own.

I hope this information is helpful, and good luck with your patient.