The only type of wild hydrangeas I ever hear of are the arborescens and then just of Annabelle. Are there others? A friends gave me a plant she has growing at her house that is a passalong plant. It likes deep shade, has hydrangea like foliage, but the leave are more burgundy and it has been blooming for awhile, and the blooms are more like sambucas, but with with many, many more tiny pink flowers packed much more densely. Also, instead of forming a shrub, it's more like individual plants. But, the leaves look just like hydrangea and are arranged like hydrangea.
I found another one on a walk in my area the other day. Too soon to tell anything about it. I dug one up (there was a whole stand of these things by the side of the road) and brought it home.
Jenny
Wild Hydrangeas
I don't think it's a hydrangea. Any chance you can take a picture and post it here? Hydrangea leaves aren't really that special and unique, so if the flowers aren't like hydrangeas then it's probably something else, there are lots of other plants that could have similar leaves.