The weeping cherry tree (Prunus subhirtella) is a prized ornamental tree defined by its gracefully cascading branches, which create a distinctive, umbrella-like silhouette. This unique form requires specialized care, making the timing and technique of pruning particularly important for maintaining the tree’s health and aesthetic. Pruning at the correct time helps prevent disease entry, minimizes sap loss, and ensures a profuse display of blooms in the spring. Understanding the differences between structural, cosmetic, and emergency cuts allows for the best long-term results.
Optimal Timing for Structural Pruning
The most appropriate time for heavy, structural pruning is during late winter or very early spring, typically between January and March. This period coincides with the tree’s deepest state of dormancy, which minimizes stress on the Prunus species. Pruning while dormant also manages the tree’s biological response to wounding, as cherry trees are susceptible to gummosis. By pruning in late winter, the tree’s internal pressures are low, reducing sap bleed and allowing wounds to begin sealing before the spring growth flush.
This timing also permits a clear view of the tree’s architecture, as the lack of leaves makes it easier to identify problematic branches. Structural pruning involves removing dead, diseased, or damaged wood, and thinning out branches that cross or rub. Removing these branches establishes a strong, open framework that allows for better air circulation and light penetration.
Seasonal Maintenance and Post-Bloom Trimming
The secondary window for light, cosmetic pruning occurs immediately after the tree has finished flowering in the spring. Performing this maintenance in late spring or early summer ensures the tree’s energy is not wasted on developing foliage on branches that will be removed. This timing also prevents the removal of next year’s flower buds, which are set shortly after the current season’s bloom.
This post-bloom trimming is intended for light shaping and controlling the length of the weeping branches. If the cascading limbs touch or drag on the ground, they should be shortened now. Reducing the branch length helps maintain the characteristic umbrella shape and prevents the tips from rotting or attracting pests.
Maintenance pruning is purely for aesthetic refinement and involves only minor cuts to the canopy’s outer edges. The goal is to preserve the natural, graceful flow of the branches while improving air movement. This lighter work is differentiated from the heavy thinning completed during the dormant season.
Techniques for Maintaining the Weeping Habit
Maintaining the weeping silhouette requires techniques focused on encouraging downward growth and eliminating upward-reaching shoots. The weeping form is often the result of a graft joining a weeping cultivar to an upright rootstock or trunk. Any growth emerging from below the graft union, known as a sucker, must be removed completely, as these will grow upright and destroy the tree’s intended form.
Upright growth emerging from the weeping scion wood, called water sprouts, should also be removed entirely back to the point of origin. These vigorous, vertical shoots compete with cascading branches and consume energy. Remove these shoots using a thinning cut, which takes the branch back to the trunk or a main limb, leaving no stub.
When shortening the weeping branches, the cut should be made just above an outward and downward-pointing bud or a smaller side branch. This heading cut redirects growth to the downward-facing bud, encouraging the branch to continue its cascading trajectory. Make the cut cleanly, about a quarter-inch above the chosen bud. Do not remove more than 25% of the total canopy in any given year to prevent excessive stress.
Handling Damage and Disease
Removing damaged or diseased wood must be done immediately upon discovery, regardless of the time of year. Delaying the removal of compromised wood allows pathogens to spread throughout the tree, potentially causing irreparable harm. This emergency pruning supersedes all concerns about bloom timing or dormancy.
Branches that are broken, storm-damaged, or show signs of disease, such as black knot galls or cankers, need to be cut out immediately. For diseased wood, the cut should be made several inches into healthy tissue below the visible sign of infection to ensure complete removal of the pathogen. This proactive removal helps the tree compartmentalize the wound and begin the healing process quickly.
It is important to sterilize pruning tools, such as loppers and shears, between cuts when dealing with known diseases. Wiping the blades with a disinfectant solution, such as diluted bleach or rubbing alcohol, prevents the transfer of fungal or bacterial spores to healthy parts of the cherry tree. The immediate removal of compromised wood is a higher priority for the tree’s long-term survival.