Flowering specimen trees such as magnolia are thoroughbred plants that are both sensitive and prone to damage that can damage branches, requiring pruning. Yet they are also sensitive to pruning and are easily injured if they are not pruned correctly. Even if there are no damaged branches to remove, careful pruning may be necessary to shape the tree or shrub and keep it looking its best.
The Magnolia Genus
The magnolia genus of trees and shrubs includes quite a large group of useful landscape species, of which there are both evergreen and deciduous types. Most of the evergreen magnolias used in landscape applications are varieties and cultivars falling with the Magnolia grandiflora species. These are typically grown in USDA hardiness zones 7 to 9. They have quite large leathery leaves and bloom in summer with large white blossoms up to 12 inches across. The deciduous magnolias used for ornamental use are generally categorized in two groups: the saucer magnolias (M. x soulangeana, M. dendata, and M. lillilora), and the star magnolias (M. koubus and M. stellata). These deciduous magnolias are typically grown in USDA hardiness zones 5 to 9 (a few are hardy in zone 4), and they bloom very early, producing white, pink, or purple blooms in early spring even before the leaves appear.
Why is this important? The methods of pruning magnolia differ slightly depending on whether your tree is an evergreen or deciduous type.
When to Prune a Magnolia
A magnolia can and should be pruned under three different circumstances:
- When the tree is planted, weak limbs and those that hinder the shape of the tree should be removed, and overly long branches should be shortened to establish a good shape to the tree as it begins growing. On evergreen varieties, remove some of the lower branches to establish good upward growth and maintain a pyramidal shape.
- Suckers, water shoots, and dead limbs should be removed whenever you notice them.
- Yearly, the tree should be examined and pruned if necessary to keep its shape proper. With evergreen magnolias, the goal is to maintain a pyramidal shape. With deciduous magnolias, the goal is to limit the size of individual branches and prevent them from becoming overly long and brittle.
Tools and Supplies You Will Need
How to Prune a Deciduous Magnolia
Prune After Planting
At planting time, use loppers or hand pruning shears, cut off any weak or damaged branches, or any that interfere with the upward symmetry of the plant. Cut the branches off about 1/4 inch above a healthy bud node or side shoot.
Remove Dead or Damaged Wood
Because a deciduous type is pruned in mid-summer to fall, dead limbs are generally easy to identify because they will be producing no leaves. Cut these limbs away using a pruning saw. Remove them all the way back to a fork. Broken branches should also be removed, again, back to a fork rather than just chopping them off below the break.
Prune for Shape
Shaping pruning should be done between mid-summer and early fall with deciduous varieties. Look for limbs that are overly long, interfering with the symmetry of the spreading growth habit, or any branches that rub together. Use lopping shears (for small branches) or a pruning saw (for larger branches) to trim back the targeted limbs to a natural fork in the branch. A ladder will be needed to reach higher branches; make sure to wear a hard hat.
To remove large branches, begin your cut about 6 inches out from the fork with an undercut on the branch. Cut about half-way through the branch, then change the saw position and begin sawing from the top of the branch, offsetting the cut about 2 inches inward on the branch. As the downward cut approaches bottom cut, the limb should neatly snap off without stripping bark from the tree
With the bulk of the branch removed, you can cut off the small remaining stump back to the fork.
Remove Suckers and Watersprouts
Whenever they appear, use hand pruners to lop off any small suckers or watersprouts that appear on the ground, trunk, or larger branches of the tree. These can be cut off flush.
To keep its attractive shape and appearance, a deciduous magnolia should be inspected yearly for shape and size. Suckers, watersprouts and dead branches should be removed whenever you spot them. Suckers and watersprouts can divert energy from the main tree, and damaged limbs can provide entry points for insects and disease.
How to Prune an Evergreen Magnolia
Prune at Planting Time
Use pruning shears or loppers to remove lower branches. Evergreen types are often tall, upright trees, and the goal is to encourage that upward growth and a pyramidal shape. Branches that are overly long should be shortened at planting time to establish a good shape right from the start.
Identifying and Removing Dead Wood
Because you are typically pruning an evergreen magnolia in the early spring, it may not be readily apparent which branches are dead, although you may have noted this the previous year. An easy way to identify living from dead branches by scraping through the bark on suspected limbs, using a sharp knife. If you find a layer of green material just under bark, the branch is living; if you find only gray or brown, the branch is probably dead.
These branches should be trimmed back to the main trunk or a fork in a major limb in order to maintain the overall symmetry of the tree.
Prune for Shape
Prune lightly in early spring for evergreen types. Pruning at this time should aim at maintaining the tree's pyramidal shape. Cut branches back to a natural fork in the tree. With large branches, prevent bark stripping by cutting first from the underside to about the halfway point, then shifting to the top side to cut down through the branch to meet the bottom cut. For convenience, you may want to remove the bulk of the branch outward 6 inches or so from the fork. Then, after the bulk of the branch is removed, cut off the short stub flush with the fork.
Remove Suckers and Watersprouts
Evergreen types are not as prone to suckering as deciduous magnolias, but when they appear, trim them off flush with the ground, trunk, or branch, using pruning shears.
Inspect your tree yearly for dead branches and to evaluate its overall shape. Most evergreen magnolias require some amount of pruning every 3 or 4 years, at a minimum.