Pruning & Training
Headed vs. Unheaded Training Presentation by Farm Advisor David Doll on trial comparing headed and unheaded trees. Trees left unheaded after the first year's growth yielded twice as much in their 3rd leaf as headed trees.
Tree Spacing, Minimal-to-No Pruning for Early and Mature Production Presentation by UC Walnut Specialist on optimal spacing for early and long-term yields. This is a long presentation, so a few important findings to note:
• When trees are younger, closer spacing will provide slightly earlier
returns (see Slide 11).
• However, when past 8th leaf, yield peaks at ~65-90 trees/ac (Slide 14),
with highest yields at ~25' across row (Slide 15), 22' within row (Slide 17).
• Ideal spacing will vary with soil type, rootstock, etc. Less-than-ideal
conditions would benefit from slightly closer spacing.
• Higher early yields are attained with unpruned trees. See Slides 23-29,
noting cumulative yield numbers in yellow. See Slide 31 for yield summary.
• Unpruned trees produced more crop per drop, with 25% more water use
efficiency than heavily pruned trees (Slide 35)