Mahonia japonica is a medium-sized, evergreen shrub that has leaves similar to those of a holly bush. The plant produces clusters of tiny yellow flower blossoms in the early winter that last until spring. After the dropping of the blossoms, clusters of light blue or black berries form that last until the next winter. Prune the Mahonia japonica plant at a point between the dropping of the berries and the development of the flower blossoms.
Locate any dead branches on the Mahonia bush that appear brown, broken or lacking leaves. Prune these limbs off as close to the base of the plant as possible using pruning shears.
Locate any tall, vertical shoots emerging from the top of the Mahonia bush that are much longer than the surrounding branches. Cut off these shoots using pruning shears until they are the same height as the remaining branches.
Crouch down and look at the base of the plant to see if it lacks leaves, which is called legginess. If the plant is bare near the ground, prune off three to four branches from the centre of the plant near the ground to promote new growth.
Prune off any additional side shoots to shape the plant into the desired appearance. In addition, remove the ends of any branches that are hanging over into other plants or blocking walkways.