Know Your Purpose for Pruning

“Don’t prune if you do not know why you are pruning,” University of California Cooperative Extension’s Craig Kallsen cautioned in a June 6 webinar about pruning navel oranges. “It’s a lot of work and thus expensive.”

“Generally, pruning of any kind reduces total fruit yield,” the citrus and pistachio farm advisor for Kern County stated. “The goal of pruning is to maintain mechanized access to the orchard for production operations and harvesting, and possibly, to improve fruit quality to increase profit.”

Kallsen said other possible reasons for topping, hedging and hand pruning orchards include:

• Control tree height or width
• Provide strong scaffolds for fruit bearing
• Increase light penetration into tree canopy
• Better pesticide spray penetration
• Reduce certain mite or insect pests or improve the environment for beneficial insects

Pruning is often less detrimental to yield if done lightly and more frequently, rather than taking a lot of outer-canopy wood off at one time, Kallsen said. He noted that citrus fruit is produced on 1-year-old wood, which is generally on the outside of the tree’s canopy.

WHY HEDGE AND TOP?
A slide titled “Why hedge?” in Kallsen’s presentation stated that hedging reduces shading of lower branches and allows equipment freer access to the grove.

Another slide stated that topping reduces shading of lower branches and keeps fruit closer to the ground. Topping can improve the harvesting efficiency of hand-picked fruit, Kallsen added.

Farming shorter trees generally means lower harvesting cost per picked carton and less risk of injury from manipulating and falling from tall ladders, he stated.

To avoid excessive shading of the lower canopy, closely spaced trees should be shorter than widely spaced trees, Kallsen said.

TREE HEIGHT RECOMMENDATIONS
Kallsen offered the following recommendations for tree height:

• Tree height should not exceed 80% of the distance from trunk to trunk in adjacent rows. For example, a 16-foot tree height would be the maximum in a 20-foot row spacing.
• The distance between outer canopy branches of trees in adjacent rows should be roughly 50% of tree height. For example, there should be 8 feet between outer canopy branches when trees are 16-feet tall.

Kallsen’s talk was the first of the Citrus Research Board of California’s 2023 Citrus Growers Educational Webinar Series being presented on Tuesdays in June.

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