The white dome hydrangea has lovely 6- to 10-inch white dome-shaped blossoms from mid-summer through fall. This shrub is easy to grow and maintain. It grows from 4 to 6 feet in height, and has a spread of 3 to 4 feet. The hydrangea can be grown in full sun to partial shade and is hardy in zone 4. The white dome hydrangea blossoms on new wood, which is important to remember when it comes to pruning this hydrangea.
Selectively cut some of the old wood down to a height of 18 to 24 inches. This will provide a framework of support for the coming season's new growth. This should be done in late winter or early spring.
Prune the remainder of the old wood down to ground level. Deposit the pruned plant material in your compost bin.
Prune to remove old blossoms. Cut just below the flower-head. Deposit the spent blossoms in your compost bin.