Evergreen magnolias -- those that retain their leaves through cool but mild winters -- should not be pruned at the same time as deciduous magnolia trees and shrubs, which is in very late winter or early spring. Wait until later in spring. Among the most common evergreen magnolias grown in the United States are the southern magnolia (Magnolia grandiflora), Chinese evergreen magnolia (M. delavayi) and in warm winter areas, the sweetbay or swamp magnolia (M. virginiana).
Pruning Time Frame
Evergreen magnolias usually require minimal pruning and rarely need annual pruning maintenance. Overzealous branch tip pruning removes tissues that produce flowers. The best time to prune evergreen magnolias is in mid- to late spring. Examine branches before pruning, noting if any flower buds are forming, as this may change your desire to remove a branch or twig. Dead or broken branches may be removed any time of year. Branches with damage resulting from heavy snow or ice storms may be cut in late winter as needed to clean up the yard.
What to Prune
Trim or lightly cut back twigs and branch tips that spoil the natural attractive symmetry of the evergreen magnolia. Errant branches that stick out awkwardly, block views to the street for safe egress or intrude into a walkway or patio are good examples of branches that need some maintenance. If desired, old flowers and developing seed pod capsules may be pruned away, a process called deadheading, to improve the appearance of the magnolia before midsummer.
Evergreen magnolias do shed leaves, especially weak or old leaves. Do not become alarmed if numerous leaves drop from the plant in spring. Usually evergreen magnolias drop their oldest leaves just before or as new leaf buds unfurl on branch tips. Avoid pruning magnolia branches after midsummer. Pruning that late in the season results in new growth in late summer and early fall that may not mature enough before the first fall frosts. Pruning magnolias when they are dormant delays wound healing.
Use sharp hand pruners to cut through woody magnolia twigs and branches that are no thicker than 3/4 inch in diameter. Branches up to 1 1/2 inches wide are best cut with loppers. Use a pruning saw to remove larger branches, making multiple cuts to lessen the size of the branch and reduce the weight load stress on the branch base where it is to be cut from the trunk. Avoid making cuts that tear or puncture the bark on the main plant.