Japanese cherry trees (Prunus serrulata and related species) are treasured ornamental plants known for their spectacular, though fleeting, spring bloom display. Maintaining the health and longevity of these trees requires a careful, specific approach to pruning that differs from many common deciduous species. Proper cutting techniques are necessary to shape the canopy, maximize flowering, and protect the tree from diseases that can significantly shorten its lifespan. This delicate species responds poorly to aggressive or mistimed cuts, making an informed strategy essential for success.
When to Prune
The timing of pruning is the most important factor when caring for Japanese cherry trees. Unlike many deciduous trees, cherry species should never be pruned during the dormant season (typically late fall through winter). This cool, damp period is when fungal pathogens, particularly the spores that cause Silver Leaf disease (Chondrostereum purpureum), are most active and easily infect open wounds.
The optimal window for pruning is during the mid-to-late summer months, generally from June through early September. At this time, the tree is in its active growth phase and can quickly form callus tissue to seal cuts. This rapid wound closure significantly reduces the risk of fungal entry and infection. Pruning immediately after the spring bloom has faded also ensures you are not removing the wood that carries the next season’s flower buds.
Assessing the Tree and Objectives
Before making any cuts, assess the tree’s health and structure to define the pruning goals. The first priority for any pruning action is the removal of wood that is Dead, Diseased, or Damaged (the 3 Ds). This sanitation process helps eliminate entry points for pests and pathogens that could compromise the entire tree.
Structural objectives involve correcting growth patterns that could cause future problems. This includes removing any branches that are crossing or rubbing against one another, as this friction damages the bark and creates open wounds susceptible to infection. The goal is also to thin the canopy to improve air circulation and allow light to penetrate the tree’s interior. Adequate light and airflow reduces humidity, an environment where many fungal diseases thrive.
Strategic cuts can also be used to manage the size and shape of the tree, such as reducing height or balancing an uneven canopy. For Japanese cherry trees, pruning is generally a process of selective removal rather than heavy reduction. The tree should maintain its natural, graceful form, and excessive cutting must be avoided as it can induce stress.
Essential Cutting Techniques
The method used to remove a branch is just as significant as the timing, as an improper cut creates a larger, slower-healing wound. Smaller branches, up to about one inch in diameter, can be removed with sharp bypass pruners or loppers, making a clean cut just outside the branch collar. The branch collar is the slightly swollen area of tissue where a branch connects to the trunk or a larger limb.
The objective is to make the final cut without damaging this collar tissue, which facilitates the tree’s natural healing process, known as compartmentalization. Cuts made too close to the trunk (flush cuts) or cuts that leave a long stub both inhibit the tree’s ability to seal the wound effectively. For ornamental cherries, the preferred technique for most cuts is called a thinning cut, which involves removing an entire branch back to its point of origin or to a lateral branch.
Thinning cuts are favored because they open the canopy without promoting the dense, bushy growth that often follows a heading cut (the shortening of a branch back to a bud). For any large, heavy branch—typically over an inch in diameter—the three-cut method should be employed. This prevents the weight of the falling limb from tearing the bark down the trunk. This method involves an undercut several inches from the trunk, followed by a top cut further out to remove the bulk of the weight, and finally, a clean third cut to remove the remaining stub just outside the branch collar.
Specialized Care for Flowering Cherries
Japanese cherry trees are members of the Prunus genus, which are prone to a condition called gummosis—the oozing of a thick, amber-colored sap from the bark. Gummosis is not a disease itself but a general stress response to injury, poor drainage, insect borers, or incorrect pruning cuts. Heavy or misplaced pruning cuts are a frequent trigger because they create a large wound the tree attempts to seal with gum.
Because these trees are delicate, drastic pruning measures like “topping” (the severe removal of upper branches) are discouraged. Topping removes too much canopy at once, causing significant stress and often resulting in an unhealthy flush of weak, upright growth. Always sterilize pruning tools with a disinfectant solution between cuts, especially when removing diseased wood, to avoid transferring fungal or bacterial spores to healthy tissue.
The use of wound dressings or pruning paint is not recommended for Japanese cherry trees. These materials can trap moisture and pathogens against the fresh cut, interfering with the tree’s natural compartmentalization process. The best practice is to make a clean, correct cut at the proper time of year and allow the tree to heal itself.