Pruning cherry trees is necessary for maximizing the tree’s longevity and annual fruit production. Since cuts are technically wounds, timing is crucial to align with the tree’s natural healing cycles and the local environment. In Washington State, where cherry production is substantial, correct timing is a factor in preventing disease and ensuring a bountiful harvest. Understanding the seasonal requirements for structural versus maintenance pruning is paramount for the health of any cherry tree.
Primary Timing for Structural Pruning (Dormant Season)
Major structural pruning occurs during the dormant season, when the tree has shed its leaves and is metabolically inactive. In Washington, this period is delayed until late winter or very early spring, typically January or February. This timing is chosen to occur after the most severe cold has passed but before the buds begin to swell with spring growth. Pruning too early can expose fresh cuts to prolonged freezing temperatures, causing tissue damage and compromising healing.
The ideal moment is just before bud break, minimizing the tree’s exposure to extreme cold and potential pathogens. Delaying cuts ensures wounds are open for the shortest time before active growth begins, initiating wound closure. This late-winter timing allows for maximum visibility of the tree’s structure without leaves, making shaping easier. Dormant pruning is aggressive and stimulates a strong flush of new growth once spring arrives.
Pruning Techniques for Health and Yield
Structural pruning involves two primary types of cuts for shaping the tree and promoting fruit production.
Thinning Cuts
Thinning involves removing an entire branch back to its point of origin, such as the trunk or a larger scaffold branch. These cuts open up the tree’s canopy, allowing sunlight to penetrate deep into the interior and improving air circulation. Increased light exposure is necessary for the development of healthy fruiting spurs, which are short, modified branches where cherry fruit is produced.
Heading Cuts
Heading involves cutting back the terminal (tip) portion of a shoot or branch. Heading cuts are primarily used on younger trees to encourage lateral branching, making the tree bushier and establishing a strong, manageable scaffold system. The goal is to train the tree into an open-center or vase-like shape, especially for sweet cherries, ensuring all parts of the canopy receive adequate light. Using thinning and heading manages tree height for easier harvesting and maintains a balance between vegetative growth and fruit production.
Regional Climate Factors and Disease Prevention
Washington State’s diverse geography, split by the Cascade Mountains, creates two distinct climatic zones influencing cherry tree care. While most commercial sweet cherry production is in the drier, colder climate of Eastern Washington, Bacterial Canker (Pseudomonas syringae) is a significant disease concern statewide. This bacterium thrives in cool, wet conditions and easily enters the tree through fresh pruning wounds, making timing crucial.
Pruning should not be performed during the wet periods of late fall or early winter, as prolonged moisture allows the bacterium to colonize open wounds. The pathogen can cause girdling cankers that kill branches or the entire tree, dictating a preference for dry-weather pruning. Delaying the main pruning until just before the spring growing season, when the tree can heal quickly and the weather is drier, is a preventative measure against this organism.
Summer Pruning and Maintenance Cuts
While structural pruning is reserved for the dormant season, a lighter round of maintenance pruning is recommended during the summer, specifically immediately following the cherry harvest. Summer pruning focuses on managing the tree’s size and controlling vigorous growth. This practice is valuable for keeping the tree at a manageable height, which makes subsequent harvests easier.
This post-harvest timing is ideal because wounds are created during the warmest, driest part of the year, significantly reducing the risk of Bacterial Canker infection. Summer cuts are minimal and include removing unwanted shoots like vertical water sprouts and suckers growing from the base or roots. Light tipping of overly long branches encourages fruit spur development for the following year. Removing a small portion of the tree’s foliage directs energy reserves toward fruit bud development rather than excessive shoot growth.