Smooth Hydrangea a.k.a. Wild Hydrangea – Hydrangea arborescens.  This white hydrangea differs from the one seen in our woods only by its rounder, dome-shaped white or pink flowers born in mid-summer.  Left alone, it forms a large suckering colony several feet tall and many feet wide.  Any variety of this species blooms on new wood so if desired it may be cut back annually in fall or early spring without sacrificing blooms, where it will stay smaller (3’ x 3’).