On occasion, the height of a hedge needs to brought down due to overgrowth, damage, light blockage or simply to refresh the look of a garden. Proper pruning limits stress on the plants that can lead to shock and preserves an attractive hedge shape. Plan to conduct severe pruning in the spring or early fall when temperatures are mild and sun or cold stress on the plants will be minimized.
Determine the desired height. If the reduction in height equals less than a third of the bulk of the plant material, you can safely make the reduction in a single pruning session. If reducing the height by more than a third of the volume, plan two or more pruning sessions with a recovery interval of several weeks in between.
Rough cut the top of the hedging plants to within a few inches above the final desired height using your scissor shears or hedge trimmers. Remove the cut plant material from the area.
Give a finished top shape to the shrub by making flat or rounded edged cuts with your shears. Hold the cutting blade parallel with the top hedge surface for a flat cut or at an angle for a curved or rounded shape. Repeat shape pruning as necessary to maintain the desired shape and height.