The Japanese barberry or berberis thunbergii autropurpurea is a deciduous broadleaf shrub that is used quite frequently in landscape design, due to its purple foliage, and low maintenance. It is often used in mass plantings, as a border, and also as a hedge. It can reach a height of 3 to 8 feet, and a spread of 4 to 7 feet, depending upon the variety. There is a drawback to this plant, though: It has extremely sharp thorns. For that reason, avoid placing it near a walkway, where small children play, or where pets may come in contact with it.
Remove any damaged or diseased branches immediately by making a clean cut at the point of the break or where it connects to a main stem. Where you make the cut will depend upon how it will affect the appearance of the plant. (Note: Diseased branches should be removed completely.) You may do this at any time of the year that you see a broken or diseased branch.
Shrubs can become damaged during the winter season due to the weight of ice and snow upon their branches. You will then prune the broken branches away in spring. Remember do not put any diseased plant material in your compost bin. And, if you have pruned away diseased plant material, disinfect your pruning shears by dipping the blades in either bleach or alcohol.
Visually inspect your bushes throughout the growing season and snip away any branches that may be interfering with the other plants in your garden bed, and also snip branches to maintain the desired shape and size (height and width) of the Japanese barberry.
Use the "heading" or the "thinning" pruning techniques. Heading cuts are made just above a side branch, and thinning cuts are made just above a bud. When you cut above a bud make your cut about ¼ inch in front of the bud. Whether you head or thin depends upon how much of the plant you need to cut away. Do this in spring while the plant is in its dormant stage, and you may also do this throughout the growing season without harming the plant in any way.
Trim to maintain a hedge by using your hedge trimmers to cut the plant to the desired height and width. This can be done every 8 weeks during the growing season. Or, you may choose to just trim the hedge in the spring and the fall. Wear gloves and safety glasses while pruning a hedge.
Prune away old, woody canes located in the center of the plant in late winter when the plant is still dormant. Removing old wood encourages the plant to produce new growth, which produces a much denser plant. Due to the Japanese barberry's sharp thorns, be sure to wear gloves.