How to Trim an Overgrown Boxwood

Remove any dead or broken branches from boxwoods as soon as you discover them. Use sharp pruning shears to cut the damaged portions slightly within the healthy growth, removing the entire affected portion. Disinfect your pruning shears between each cut by dipping them in a bucket of solution that contains one part of chlorine bleach and nine parts water. This helps minimize the spread of disease.

Thin out thick foliage to allow light and air to reach the inner growth. Early winter is the best time to perform annual thinning of boxwoods, although you can perform this task any time of the year. Grasp an inner branch and cut about 6 inches off the tip of the twig. Cut about 10 percent of the outer branches in this manner, spacing your cuts evenly throughout the boxwood shrub.

Shape boxwood shrubs beginning three years after planting. Create the desired shape by cutting about half of the amount of branch length you intend to remove. Keep the bottom slightly wider than the top to encourage even sunlight exposure. Work your way around the shrub, making these shallow cuts along all the outer vegetation. Stand back and view the shape and appearance of the boxwood shrub or hedge. Clean up the outline by removing additional lengths of branches that extend beyond the desired shape.

Stand back and view the shape again to make sure it looks uniform from all angles. Prune the entire shrub or hedge down to the desired size by taking the same amount of length off all the branches. This helps you create an initial shape that is even and balanced, rather than trimming too much from any one section.