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Minimum Pruning

Minimal Pruning Techniques to Develop Almond Orchards

John Edstrom, Bill Krueger
UC Farm Advisors

Almond tree training and pruning practices haven’t changed all that much for decades. Standard pruning concepts stress careful selection of primary and secondary branches to develop strong evenly spaced branches capable of supporting heavy crops over 30-40 years. Yearly pruning was recommended to stimulate growth on old trees and to manage light. Considerable time and expense ($100/ac +) are required to complete this type of pruning operation if the weather cooperates.

 

Today, many growers don’t expect orchard to produce longer than 25 years. Economics are changing rapidly and new varieties/ rootstocks/technologies are being developed.

 Tree densities have increased to 100+ trees/ac, twice what they used to be. These smaller sized trees don’t need to support such heavy weights per tree nor is limb position as critical to develop large expansive canopies. Yearly pruning becomes less important to stimulate growth in younger trees or to allow sufficient light to filter down into shorter trees for flower bud formation. In this new situation, adjustments may be needed in tree training and pruning to maximize future profitability.

A field test was set up in 1997 at Nickels to evaluate various experimental training systems for future almond orchard development. Included also is a treatment to evaluate the nonpruned technique tried in the hedgerow planting on the Green Bay Nickels orchard during the eighties.

Four training systems are being evaluated (4 replicates of 33 trees for each type on Nonpareil, Carmel, Monterey and Aldrich) planted on slip plowed ground at a 16' x 22' spacing.

 

Color Code
None Standard Three Primary limbs selected at 1st dormant pruning, secondaries selected 2nd dormant, centers kept open, limb tying/staking as necessary. Yearly moderate pruning as needed.
White Unpruned Three Primary limbs selected at 1st dormant pruning the no additional pruning unless needed for equipment for wind damage, etc. Minimal staking as necessary.
Blue Mechanical Hedged Same as unpruned but adding machine topping to remove most of prior season’s top shoot growth beginning at 2nd dormant and then yearly.
Orange Temporary Scaffolds Train limbs at 1st dormant to favor 3 standard permanent scaffolds as above, but also retain many other temporary branches below these on trunk removing only those which compete with permanent scaffolds. Open centers normally, stake, etc. Temporary limbs intended to be removed year 5-8 after producing some crop or sooner if they threaten primaries (most should at least contribute to larger tree/root size).

 

Results:

Trunk size measurements taken 18 months after planting showed a slight size increase for trees with temporary limbs. All others were equal in size. During April, 1998, strong northerly winds damaged most local 2-3 year old orchards. Many primary limbs were broken in the test plot. However, trees with temporary scaffold training experienced no limb breakage while all other training methods resulted in significant breakage.

 

#4 Temporary:

Nonpareil scaffolds developed satisfactorily even with competition from the temporary limbs. Some removal of upright growth on temp limbs needed to deinvigorate these branches and a few temp scaffolds needed complete removal to insure permanent scaffold and secondary limb development. (This system may work best if 1 inch trees used at planting and headed quite high at 40 inches. This would give enough room for permanent scaffold development on top and for temporary scaffold positioning on trunk leaving room for shaker head to grab trunk below pruning wounds left after temp limbs removed.)

Carmel and Monterey varieties were somewhat more difficult to train using the temp scaffold idea. More flattening and removal of temp limbs were necessary to maintain the dominance of permanent primary limbs.

The upright growth habit of the Aldrich variety does not appear compatible with the temp scaffold technique. The temp limbs competed severely with the permanent scaffolds and were completely removed at the 2nd dormant pruning.

 

#3 Mechanically Hedged:

Trees of all 4 varieties were topped removing 2/3rds of past season’s top shoot growth with the intention of developing a more compact, dense tree shape. More was removed from the taller Nonpareil and Aldrich plots than the Monterey and Carmels. Some dormant hand pruning will be needed to thin excessive branches and open center.

 

 

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Copyright © 1999 Colusa County Cooperative Extension, Univ. of California
Last modified: September 01, 2000