Pruning fruit trees is necessary for maintaining tree health, maximizing fruit production, and managing tree size for easier harvesting. In Northern California, the timing of this practice is highly dependent on the region’s diverse microclimates, which range from the cool, foggy coast to the hot, dry inland valleys. Proper timing is a physiological decision that determines whether the tree puts energy into vigorous vegetative growth or focuses on fruit-bearing structures.
Structural Pruning During Dormancy
The primary window for heavy, structural pruning of most deciduous fruit trees, such as apples, pears, plums, and peaches, is in late winter. This timing corresponds to the period when the tree is fully dormant, having shed its leaves and stored its energy reserves. Specifically, growers in Northern California should aim for January through early March, just before the buds begin to swell. Pruning during this late-dormant phase encourages a strong, vigorous burst of new growth when the spring growing season begins.
The goal of this winter work is to establish the tree’s foundational structure, removing damaged, diseased, or crossing branches to create an open canopy. An open structure allows for maximum sunlight penetration and air circulation, which aids fruit ripening and disease prevention. Depending on the tree type, this structural pruning involves significant cuts; for instance, fast-growing stone fruits like peaches and nectarines often require the removal of up to 50% of the previous year’s growth to renew fruiting wood.
Pruning too early, in the late fall or early winter, reduces the tree’s natural cold hardiness. Cuts made before the tree has fully acclimated to cold temperatures can make the pruned wood more vulnerable to freezing injury, especially in colder inland valley areas. Waiting until the coldest part of winter has passed, but before the tree awakens, minimizes the risk of exposing fresh wounds to frost and disease pathogens.
An exception to this late-winter rule involves apricots and sweet cherries, which are susceptible to the fungal disease Eutypa dieback. This fungus infects pruning wounds during rainy, cool weather, which is common in Northern California winters. To avoid this, major cuts on these stone fruit varieties should be shifted to a dry period in the summer, directly after harvest. This delay allows the wounds to dry and compartmentalize quickly, reducing the risk of fungal entry.
Maintenance Pruning in Summer
Summer pruning serves a different purpose than the heavy structural cuts of late winter, focusing on maintenance and growth management. This lighter pruning is typically performed from late spring through mid-summer, generally between June and July. The physiological response to summer pruning is to slow down growth, which is useful for controlling the size and height of vigorous trees.
This practice involves removing upright, non-fruiting water sprouts and thinning new growth in the tree’s canopy. Removing this foliage improves light penetration to the inner branches and developing fruit, which enhances fruit color and sugar production. For backyard growers, summer pruning is an effective method for keeping trees to a manageable height, making harvesting and maintenance easier. Unlike dormant pruning, summer cuts should be light, generally removing no more than 20% to 30% of the foliage, to avoid stressing the tree.
Pruning Citrus and Evergreen Varieties
Fruit trees that do not enter a full dormant state, such as citrus, avocados, and olives, require a different pruning schedule. These evergreen varieties are sensitive to cold, so significant pruning must be postponed until the danger of frost has reliably passed. In Northern California, this means pruning should be done in the late winter or early spring, typically from March through May.
Pruning citrus trees focuses primarily on removing dead, diseased, or damaged wood, as well as thinning dense growth to improve air circulation. The best time to make these cuts is right after the main harvest, which often aligns with the late winter or early spring window. This timing allows the tree to recover and put energy into the next flush of growth before the summer heat arrives.
For evergreen trees like avocados, pruning is generally minimal and aims to shape the tree or remove low-hanging branches. Olives are often pruned after harvest to manage height and encourage new fruiting wood, but this must also occur after the frost risk has ended. Trees like figs, while technically deciduous, are also best pruned toward the end of their dormant season, in late winter, to prevent sap loss. The overarching rule for all evergreens is to avoid making substantial cuts in the fall or mid-winter, as new growth stimulated by the pruning would be vulnerable to unexpected cold snaps.