This description is for Hydrangea arborescens: Hydrangea arborescens is a medium-sized shrub that is perfect for small, woodland gardens in particular. The deciduous plant is also know by several easier to remember names, such as Smooth Hydrangea or Sevenbark. This is a great plant for those of you who like to admire your garden rather than working on it, as its sturdy nature means that it needs minimal attention in order to grow and flourish. Smooth Hydrangea produces striking blooms of white flowers that bring colour to any small garden. The shrub requires minimal pruning in late winter or early spring, and grows to between four and six feet in height.