It happens sometimes with paniculatas in the summer. They "show their feet" due to heat and soil moisture problems.

Once temps moderate in the Fall, they may put new growth but more likely, they will develop new leaves in the Spring instead.

Make sure they are well mulched year around so the soil moisture does not evaporate. Remember to increase the amt of water per watering in the Summer and, to prevent overwatering, make sure you water the soil when it feels almost dry or dry to the touch if you insert a finger to a depth of 4".

Where are you? Can you post a photo? Is this a new planting this year? How plants behave is usually dependent on their age, growing conditions and the particular variety, and Luis's extensive experience growing Hydrangeas in TX are quite different from what I see in my garden in NH. I do agree with his comments on mulch and watering, but find here that even in drought years my H. paniculata bushes need next to no supplemental water, even in all day sun.

If it continues to do this, you might want to do what Hyed has done with a Vanilla Strawberry - trim it to tree form as pictured part way down this thread.

Here's how to add location info to your profile so it posts automatically:

Go to Your Houzz in the upper right of every page, click Edit Profile, and on the left side click advanced settings. Well down the advanced settings page is a blank labeled Climate Zone for Garden Forums along with a link to find your zone.

If you add info on your state or the nearest large city you will get even better information since zone only relates to average coldest winter temperatures.

Then return to the top of the page and click Done Editing.