Magnolia trees, a favourite ornamental planting of many home gardeners, can benefit from an occasional light pruning. Pruning a magnolia in summer after the tree flowers usually gives the best results. Magnolias typically bloom before June from buds that developed in the previous year. If you prune them in the spring or winter, you might prevent the tree from flowering. Magnolia rarely need heavy pruning. A light maintenance pruning once a year should suffice.
Begin pruning after the tree blooms. Use a hand pruner for branches less than 1/2 inch in diameter. Use a lopper for branches greater than 1/2 inch in diameter and for the largest branches use a pruning saw, advises the University of Kentucky Extension.
Cut back any diseased or dead branches with loppers. Cut the branches about 1/2 to 2 inches above where the branch and the main stem of the tree intersect, called the collar. Make a clean cut and do not leave a stub, which can leave an opening for disease. Start your pruning among the higher branches of the tree and work your way down to the lower branches.
Remove branches rubbing against other branches. Prune the branch that looks the least healthy when two branches that rub each other.
Prune suckers from the base of the tree with pruning shears. Remove any water spouts, fast-growing vertical branches.
Avoid cutting back any more branches than absolutely necessary. Magnolias rarely need or respond well to a heavy pruning. If you must prune a tree to reduce it size, cutback a few of the tallest or most widespead branches rather than cutting back all the branches into a circular shape, advises the London newspaper "The Telegraph." This helps the tree keep its natural shape.
Inspect your magnolia for water sprouts buds occasionally. Take them off manually when you find any.
Avoid making large pruning cuts into live older branches, if possible. Magnolias often heal slowly from such wounds.