Flowering specimen trees such as magnolia are damage-prone thoroughbred plants, requiring occasional pruning of branches. 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. But it's important to remember that magnolias are quite sensitive to pruning and easily injured if they are not pruned correctly. Too much pruning of the canopy, and a magnolia can be sunburned.
Before Getting Started
Before pruning your magnolia, ensure that you know what type you've got. 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 within 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 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.
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 or damaged limbs should be removed whenever you notice them.
- On a yearly basis, the tree should be examined and pruned if necessary to keep its proper shape. 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. Shape pruning generally occurs in mid-summer to fall for deciduous types, in early spring for evergreen types.
Equipment / Tools
- Ladder (usually a stepladder will suffice)
- Hand pruner
- Pruning loppers
- Pruning saw
- Hard hat
How to Prune a Deciduous Magnolia
Prune After Planting
At planting time, use loppers or hand pruning shears to 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, 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.
Magnolia wood is extremely heavy—much heavier than it appears. Cut small pieces you are confident you can handle before you you start making larger cuts.
Prune for Shape
Pruning for shape 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 halfway 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 the 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 water sprouts that appear on the ground, trunk, or larger branches of the tree. These can be cut off flush.
How to Prune an Evergreen Magnolia
Prune at Planting Time
Immediately upon planting, 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.
Identify and Remove 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 is by scraping through the bark on suspected limbs, using a sharp knife. If you find a layer of green material just under the 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.