Magnolia Grandiflora Pruning

Magnolia grandiflora is commonly called southern magnolia, although it grows in U.S. Department of Agriculture plant hardiness zones 7 through 10. Known for its showy, fragrant flowers, these large evergreen trees typically require little in the way of pruning or maintenance. However, there are occasions when it may become necessary to prune a magnolia, and if done right, it should keep your tree healthy without any long-term damage.

Magnolia Grandiflora

There are two classes of magnolia, deciduous and evergreen, and the southern magnolia is of the latter type. The tree's leaves are smooth, shiny and almost leathery, while the flowers are cup-shaped with white blossoms that come and go throughout the summer and into fall. A typical southern magnolia averages 50 feet in height and rarely grows to over 100 feet. Magnolias are favorites as both an ornamental and a shade tree, and if left unpruned, the lower branches of the tree will sweep to the ground. The southern magnolia tends to be less cold-hardy than other species like the sweet bay magnolia.

Reasons for Pruning

Southern magnolias are soft-wooded and may be prone to breakage in ice storms or suffer other winter-related damage that will necessitate pruning dead branches. Magnolia branches are also susceptible to canker diseases and verticillium wilt. Remove branches that cross or rub against other branches, as the rubbing can cause open wounds and allow diseases and insects to get inside the tree. Other reasons you may need to prune magnolias include the large drooping canopy affecting car or pedestrian traffic or a patio or walkway underneath. Southern magnolias can also be pruned to be used as espaliers, so that they grow flat against a wall, fence or trellis.

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Prune a magnolia only when necessary, since they can bleed from pruning wounds. Magnolias can also be slow to heal and not make new growth until the second season after pruning, so avoid large cuts into old wood if possible. The time to prune a magnolia is after blooming during the growing season in spring and through the summer. Pruning them in midsummer will give them time to heal before winter, since dormant magnolias don't heal easily.

How to Prune

When pruning your magnolia, remove the entire twig or limb down to its base. Don't leave a stub that can produce weak stem suckers and make it easier for pests and diseases to attack the tree. Don't paint or tar pruning cuts because it interferes with the plant’s own wound defense system. The only tool you will need for the task is a high-quality hand clipper for branches less than 1/2 inch in diameter, a lopper for branches up to 1 and 1/2 inch, or a pruning saw for the largest branches. Make sure blades are sharp to leave smooth cuts that heal faster and reduce disease problems. If you're pruning to remove an infestation, sterilize the pruning tools by dipping them into undiluted alcohol or a solution of 10 percent bleach.


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