Answer: In order to make seed heads, flowers have to be open long enough for insects to pollinate them; and, hydrangea flowers are sterile and won't set seed. So, you may be indentifying something that isn't really there. If the flowers on your hydrangea are not opening fully (which I suspect is the case), your plant either got a late frost or it is not getting enough sunlight. Annabelle hydrangea is one of the hardiest of all hydrangeas and they bloom on new wood of the season. Pruning it down in early spring encourages lots of new growth and each of those new stems will produce a flower. I'd cut off the spent flowers and hope your plant produces more flowers later in the summer.
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