White flower heads up to a foot across open in early summer on this smooth hydrangea, a wild form found near Anna, Illinois and in gardens since the 1960s. Hydrangea arborescens 'Annabelle' grows 3 to 5 feet tall and 4 to 6 feet wide in part shade, hardy from Zone 3 through Zone 8.
The heads open pale green, turn pure white, and age back to green by late summer, and the dried heads stay on the plant into winter. It flowers in one long flush, and cutting off the spent heads can bring a lighter second round.
Smooth hydrangea, Hydrangea arborescens, is native to the eastern United States and is one of the hardiest garden hydrangeas, reliable into Zone 3. It flowers on new wood, forming its buds in spring on the current year's growth, so a hard winter or a late frost does not cost it a season of bloom. Soil pH does not change the flower color.
Cut the stems back to about 18 inches in late winter or early spring, before new growth starts, and the plant flowers the same summer on the growth that follows. Leaving that framework rather than cutting to the ground builds thicker stems to carry the flower heads. Smooth hydrangeas need steady moisture, tolerate wet ground, and do best with shade from midday on where summers run hot. Deer do browse them.
The wide spread fills a mass planting, a shaded border, or a low spot that stays damp.
