Buckthorns are a sizeable family including redberry, coffeeberry and several types of buckthorn, such as Italian or cutleaf. Pruning is recommended to shape the trees or shrubs, and otherwise isn't absolutely necessary. Pruning should generally be done during the tree's dormant stage, to reduce trauma and injury, and encourage future growth. Hedge buckthorns may be trimmed more often.
Choose the right time to prune. This depends on your local climate, but should be between late fall and early spring. It's often easier to prune after winter sets in, for ease of shaping and cleanup, but it can be done any time after the tree has gone dormant for the winter. Southern tree owners often prune in early spring to stimulate early growth.
Use sharp garden shears, to reduce tearing and shredding of the plant. Electric trimmers can be used on hedges, but result in more breakage than hand shears do. Cut away any dead or diseased wood, and for trees, cut to shape as desired. For hedges, cut shorter than desired; as much as a foot down for young hedges. Keep in mind that often, where you cut will be the site of new growth.
There is an additional step for columnar buckthorn; to maintain upward shape and growth, prune out about one-third of the oldest and thickest branches at the base. Choose random branches, but spread them out evenly around the circumference of the tree so as not to make it lopsided. Use a pruning saw for large branches.
If you are pruning a buckthorn hedge, consult your local agriculture extension agency. Some varieties of buckthorn are considered invasive in some areas. They may ask that you keep your buckthorn pruned regularly so as to eliminate flowers and berries that will cause the plant to spread throughout your neighborhood. If you want to keep the buckthorn from reproducing, prune every three to four weeks.
You also can do minor pruning of buckthorn trees and hedges periodically throughout the summer growing season, to maintain shape and size if desired. Use the same pruning method, but cut less, just trimming unwieldy growth where needed.