Magnolia shrubs are admired for their impressive flowers, which often signal the arrival of spring or summer. While these plants generally develop a beautiful, natural form without much intervention, occasional pruning is necessary for their long-term health and to maintain a manageable size. Magnolias are slow to heal, so the philosophy is to prune minimally, but with precision when a cut is needed. This guide will provide the specific details required to prune your magnolia bush successfully, ensuring a healthy plant and abundant blooms in the following seasons.
The Critical Timing for Magnolia Pruning
Correct timing is the single most important factor when pruning a magnolia, as making a cut at the wrong time can eliminate the next season’s flower display. Magnolias bloom on “old wood,” meaning the flower buds for the next year are formed shortly after the current year’s flowers fade. For the common deciduous varieties, which bloom in early spring, the optimal window is immediately after all the petals have dropped, typically in late spring or early summer.
Pruning during this post-flowering period gives the plant maximum time to develop new buds before the dormant season. Pruning in late winter or early spring should be avoided, as this will remove the already-formed flower buds, resulting in a year without blooms. Making cuts during the dormant season can also cause the magnolia to “bleed” sap, which can stress the plant and attract insects. Evergreen varieties, like Magnolia grandiflora, are often best pruned in spring as new growth begins.
Necessary Equipment and Preparation
Before making any cuts, you must gather the appropriate tools and ensure they are properly prepared. You will need sharp bypass hand pruners for branches up to about three-quarters of an inch in diameter. For thicker branches, use long-handled loppers, and a pruning saw is required for any wood that exceeds one and a half inches across. Using sharp, correctly sized tools minimizes injury to the plant, promoting faster healing.
It is important to sterilize your cutting tools before and between pruning different plants to prevent the spread of diseases. A simple and effective sterilization method is wiping the blades with 70% isopropyl alcohol or a solution of one part household bleach to nine parts water. Always clean off any sap or debris first, and wear protective gear like gloves and safety glasses during the process.
Specific Pruning Techniques for Health and Shape
The first priority in any magnolia pruning session is to remove dead, damaged, or diseased wood, which can be done at any time of year without risking the flower buds. Dead branches are brittle and dry, while diseased wood may show discoloration or cankers. When removing these, cut the branch back to a point just above a healthy, outward-facing bud or where it meets a main branch, ensuring the cut is made into healthy wood.
Structural pruning involves two main types of cuts: thinning and reduction. These techniques are essential for managing size, directing growth, and maintaining the plant’s overall shape.
Thinning Cuts
Thinning cuts open up the canopy, which is important for improving air circulation and allowing light to penetrate the shrub’s interior. This is accomplished by removing an entire branch back to its point of origin at the main trunk or a larger branch. Cut just outside the swollen area known as the branch collar. These cuts encourage growth on the remaining limbs and maintain the plant’s natural, open form.
Reduction Cuts
Reduction cuts are used to shorten a branch and direct new growth for shaping or size control. To make a reduction cut, identify a strong, healthy bud or a lateral side branch growing in the direction you want the new growth to take. Cut the branch approximately one-quarter inch above this bud or side branch at a slight angle that slopes away from the bud. Avoid leaving a long stub, as this tissue will die back and can create an entry point for disease.
When attempting to reduce the overall size of the magnolia bush, avoid aggressive cuts or “topping” the plant, as magnolias respond poorly to severe pruning. Instead, reduce the size gradually by making thinning and reduction cuts to selected branches over several seasons. The goal is always to reduce the overall mass while retaining the plant’s natural structure. Finally, remove any vertical water sprouts or suckers growing from the base or along major branches, as these fast-growing shoots draw energy away from the main structure.