Hydrangea

Smooth hydrangea is the native species that produces enormous, rounded flower heads, up to twelve inches across in the best selections, in white or soft green, on a compact, deciduous shrub that dies back to the ground each winter and rebuilds from the roots. 'Annabelle' is the cultivar that made this species famous: massive, snowball-like clusters that weigh the branches down after rain and turn green as they age. 'Incrediball' was bred to hold its heads upright on stronger stems. Native to the eastern United States, it grows three to five feet tall with a rounded, suckering habit.

The critical advantage of smooth hydrangea in Western Washington is that it blooms on new wood. Prune it to the ground in late winter and it flowers on the current season's growth, no worrying about protecting last year's buds through a late frost. This makes it the most foolproof hydrangea for the region. Sun to part shade and moist, well-drained soil produce the best performance. It also tolerates rain gardens and low spots better than bigleaf hydrangea. No significant disease or pest concerns are tracked. The flowers start white, age to green, and dry to tan, providing interest from July through the winter if you leave the heads standing. For a hydrangea that blooms reliably every year regardless of winter weather, smooth hydrangea is the safe choice.