Winter pruning of fruit trees

We’re fortunate to live in California’s Central Valley—one of the most fertile agricultural regions in the country—and thus we have the ability to grow a huge variety of fruit- and nut-bearing trees. Stone fruits (apricots, cherries, nectarines, peaches, plums), pome fruits (apples, pears, Asian pears), nuts (almonds, walnuts, pecans), and others (figs, persimmons) all do very well in our climate and soils.

Knowing how and when to prune these types of trees is essential to their successful establishment, their long-term health, and their productivity.

Careful, purposeful training of fruit trees during their first few years of life after planting is crucial to having a well structured, healthy, and high-yielding tree in later years. Generally speaking, fruit trees should be trained to have a few main branches that emerge low on the trunk, for easier access when pruning and fruit-picking, at a 45 degree angle for good strength. These main or “scaffold” branches should form an open, un-crowded framework, to allow for proper sun exposure and air circulation within the tree. Shaded and/or crowded branches will eventually stop bearing fruit.

Fruit trees can be trained into several forms: vase-shaped, central leader, Y, or espalier. The pruning methods and timing for creating these forms vary and is too complex to cover in detail here. Consult one of the sources listed below if you have a young new fruit tree and want to know how to effectively “parent” it during its adolescent and teenage phases.

Mature, deciduous fruit trees—those fully grown trees that lose their leaves and go dormant during the cold winter months—can be pruned during the months of December, January, and as late as mid-February, while their branches are bare. Late January is our best month for pruning deciduous fruit trees, since it’s well into the dormant season but before the buds begin to swell. Avoid pruning on foggy or rainy days or when the trees are moist, since damp conditions can spread pathogens into freshly cut wood.

Depending on the kind of fruit tree, between 20% to 50% of the prior year’s growth should be removed to encourage the best fruit production. Consult the references mentioned below for specific recommendations.

(Image courtesy of UCANR)

When pruning, pay close attention to the location of the buds along the branches. All pruning cuts should be made no more than ¼-inch beyond a bud; don’t leave long stubs of branch without buds. Also pay attention to the orientation of the buds; they produce growth in the same direction they point, and it’s best to end the branch with an outward facing bud. New branch growth emerges at the location of the cut (not closer to the trunk), and the more buds cut off the end of the branch, the more vigorous the new growth will be.

Some types of growth should be removed completely: dead wood, damaged or diseased branches, suckers (small, vigorous, weakly-attached sprouts that emerge from the root line or trunk), downward growing branches, or branches that cross over others. When removing entire branches, make the cut at the attachment point but just beyond the ring of thickened tissue at the base of the branch; preserving this “branch collar” will help maintain the tree’s ability to heal itself. Don’t leave long stubs, and allow cut surfaces to dry out and seal naturally.

Fruit trees can also be pruned during the growing season while leaves are still on the tree. However, this should only be done under limited circumstances, such as to train a young tree or to slow or correct the growth of a too-vigorous or overgrown older tree. Do this type of pruning in late summer after fruit has been harvested.

One principle to remember when pruning actively growing trees, whether fruit or other: don’t remove more than one-third of the crown (the upper,  leafy part of the tree) at a single time.  When pruning mature leafy fruit trees, it’s best to remove no more than one-tenth of the overall growth. The leaves are where the process of photosynthesis occurs, and if too many leaves are removed at once, the tree’s capacity to produce its own food (carbohydrates) and your food (fruit) is drastically reduced. This in turn will cause a significant portion of the tree’s root system to die, which makes the tree more susceptible to underground fungal infection, internal rot, and even death after a few years. 

Another very important caveat is to use well-maintained pruning tools. Cutting plant stems or branches with dull and dirty hand pruners, loppers, or pruning saws is the equivalent of performing an operation with rough-edged, unsterilized surgical implements. Neat and clean pruning cuts help prevent excessive damage to a tree’s living tissues, and that in turn allows the tree to heal its wounds and recover quickly.

Using hand pruners to remove an inward growing branch on a fruit tree (UNANR)

Before you head out into the garden for your annual fruit tree maintenance project, grab a sharpening stone and use it regularly and frequently as you shape your treasured trees. Remove dirt and debris from pruning tools and scrub them with hot soapy water both before and after use, to keep them and your trees in good condition.

Disinfection of pruning tools is usually recommended only when working on diseased trees or shrubs. This can be done by soaking tools for at least one minute in a solution of 1 part denatured alcohol to 9 parts water, or by spraying them with a household aerosol disinfectant. 

These wintertime pruning recommendations do NOT apply to citrus trees: oranges, tangerines, lemons, limes, grapefruits, kumquats, etc. Citrus trees are evergreen (keeping their leaves year-round) and they don’t need regular, annual pruning. If citrus trees need thinning, do it in warm weather: either in the spring before trees bloom, or in late summer after harvest. This prevents any tender new shoots from being damaged by winter frosts or frigid winds.

For those of you who want to grow trees that reward you with homegrown, healthy food, here are a few great resources:

  • The Home Orchard: Growing Your Own Deciduous Fruit and Nut Trees, by the University of California, Agriculture and Natural Resources (UCANR) — UCANR Publication 3485. This book was written specifically for backyard orchardists, and it covers a full range of helpful topics, from the planting and care of young trees to the pruning and harvesting of fruit from mature trees.
  • Growing Your Backyard Orchard (http://sjmastergardeners.ucanr.edu/Growing_fruits_in_your_backyard_orchard/), a webpage of the San Joaquin County Master Gardeners. This site has links to a wealth of information, including several publications about pruning fruit trees of different ages and conditions; calendars of operations for different types of fruit and nut trees; information on pests and diseases; fruit preservation guides; and much more.
  • Fruit Trees: Training and Pruning Deciduous TreesUCANR Publication 8057 (http://homeorchard.ucdavis.edu/8057.pdf)
  • Peach Leaf CurlUCANR Publication 7426 (http://ipm.ucanr.edu/PDF/PESTNOTES/pnpeachleafcurl.pdf). This fungal disease causes severe leaf distortion on peach and nectarine trees; post-pruning treatment with an appropriate antifungal spray is recommended during the dormant season.
  • An Illustrated Guide to Pruning, by Edward F. Gillman. This is an exhaustive and beautifully illustrated manual on anything you’d ever want to know about pruning trees and shrubs. Widely used as a horticultural textbook, it’s also an invaluable reference book for both homeowners and landscaping professionals.
  • Winter Fruit Tree Pruning 2012 (https://www.youtube.com/watch?v=EpU8W-H5xZ4).  This video by Dave Wilson Nursery, although not an endorsement, provides a very good visual overview of early fruit tree pruning.

Whether you have only one fruit tree, are beginning to plant a home orchard with many different trees, or have several established trees, use the late fall and early winter months and these excellent reference guides to prepare for upcoming pruning tasks, and then enjoy a bountiful harvest in 2020.

For gardening-related questions, call the UC Master Gardener office at 209-953-6112, or visit our website: http://sjmastergardeners.ucanr.edu/.

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