The smooth hydrangea is a rounded shrub that suckers readily. Growing to 5 feet by 5 feet after just a few years, it is one of the fastest growing shrubs available. It is a nice small shrub for naturalizing in a shaded border. The flowers of the species are flattened clusters of small inconspicuous flowers with a ring of larger fertile flowers. The species is not showy and is rarely grown. Several cultivars have been developed with much more attractive flowers. A distinctive feature of this shrub is its long-lasting flowers in dense clusters 4 inches to 6 inches across that pass from green to white in color during the blooming period of late June and July, then changing to light green again and eventually brown by September. This is an old-fashioned favorite.