Gardeners should prune oakleaf hydrangeas annually, in autumn or early winter, immediately after they bloom. The amount of plant growth in the previous season determines how much they bloom, so gardeners should only remove up to one-third of their growth.
Oakleaf hydrangeas, which produce white and pink flowers, just need light trimming. Using pruning shears, the gardener makes sharp cuts where each branch intersects with the main plant stalk. He looks at the overall plant shape between cuts and trims every side to maintain a balanced appearance. The plants keep their shape better when they are pruned minimally. Whenever gardeners see diseased, dead or broken branches, they should remove them; otherwise, the shrub's system may become weakened.