The fruitless mulberry (Morus alba ‘Fruitless’ cultivars) is a widespread choice for landscape planting because of its rapid growth rate, providing dense shade quickly. This cultivar, a male form of the white mulberry, does not produce the messy fruit of its counterpart but retains the species’ vigorous growth habit. To manage the tree’s size and prevent the development of weak structural wood, a regular and heavy pruning regimen is necessary.
Why Pruning is Essential and When to Do It
Pruning is necessary to ensure the long-term structural integrity of the fruitless mulberry. The tree’s fast growth often results in wood that is brittle and prone to failure, especially in high winds or under the weight of ice or snow. By selectively removing excess growth, you reduce the overall mass of the crown, which prevents potential limb breakage and maintains a safe structure.
The ideal time for major pruning is during the late winter or very early spring, just before the tree breaks dormancy. Pruning during this window minimizes the tree’s stress and reduces the risk of excessive sap flow, commonly referred to as “bleeding,” which is a notable characteristic of mulberries. Although sap loss is generally not harmful to the tree’s health, pruning at this time ensures that the tree’s energy reserves are fully available for rapid wound closure once the growing season begins.
Preparation and Necessary Tools
A successful and safe pruning job starts with having the right tools for the varying branch sizes. You will need bypass hand pruners for cutting small branches up to about a half-inch in diameter, which allows for clean, precise cuts. Loppers are used for branches up to about one inch in thickness, providing the leverage needed to cut through medium-sized wood.
For any branch thicker than an inch, a specialized pruning saw is required to make the cut without damaging the surrounding tissue. Before beginning any work, all cutting tools should be cleaned and sterilized, typically with a solution of diluted bleach or rubbing alcohol. Sterilizing the blades prevents the accidental transmission of fungal or bacterial diseases to the fresh wounds on your mulberry tree.
Step-by-Step Pruning Techniques
The initial focus of the pruning process involves cleaning the canopy by removing all dead, diseased, or broken branches. Next, address any crossing or rubbing branches, as this contact point creates wounds that become entry sites for pests and pathogens. These initial cuts help to improve air circulation and light penetration throughout the crown, which is beneficial for overall tree health.
Structural pruning involves two main types of cuts: thinning and heading. Thinning cuts remove an entire branch back to its point of origin on the main trunk or a larger lateral branch, which opens the canopy without stimulating dense, unwanted regrowth. Heading cuts shorten a branch back to a smaller, healthy lateral branch or a dormant bud to direct growth and limit the tree’s size.
For removing any large, heavy branches exceeding one or two inches in diameter, the three-cut method is required to prevent bark stripping. The first cut is an undercut made on the branch’s underside a few inches from the trunk. This is followed by a second cut made from the top further out on the branch, which removes the bulk of the limb’s weight. The third and final cut then removes the remaining stub, placed precisely just outside the swollen area known as the branch collar, which contains the tree’s natural wound-healing tissue.
Maintaining the Tree’s Shape and Managing Aggressive Growth
Due to the tree’s inherent vigor, the fruitless mulberry often produces two types of aggressive, unwanted growth: suckers and water sprouts. Suckers are shoots that emerge directly from the tree’s root system or the base of the trunk, while water sprouts are fast-growing, vertical shoots that appear on the main limbs or trunk. Both types divert energy from the desired canopy growth and are often weakly attached.
These shoots must be removed immediately upon sight throughout the entire growing season, not just during the dormant pruning period. Suckers should be traced back to their origin point on the root or trunk and cut off cleanly, which is more effective than simply tearing them away. Consistent removal of water sprouts and suckers is the most effective way to maintain the tree’s established shape and prevent the rapid, unsightly development of dense, vertical growth.