Adapted from “Pruning and training young almond trees” and “Tying Young Trees” by Joe Connell, UC Farm Advisor, Butte County in the Sacramento Valley Almond News, January 2012 and April 2013, respectively.
The more you prune a tree the lower the yield will be and the less you prune the heavier the yield. But this does not mean that you shouldn’t prune almond trees. The dormant pruning done to an almond tree after its first and second growing seasons is the most important it will ever receive.
Identify primary scaffolds with good angles of attachment for structural strength, selecting three scaffolds spaced vertically and horizontally around the trunk. Avoid poorly attached branches with included bark (Fig.1). These three primary branches permanently establish the tree’s basic frame. Leaving more than three limbs often results in poor crotches, weak branch attachment, and excess breakage when the first big crop is set, particularly on vigorous rootstocks.
Figure 1. A weak primary scaffold with included bark (left) that is likely to split out. A primary scaffold with strong branch attachment (right).
From UC trials we know short pruning in the first dormant season – heading scaffolds back to 12 inches and stripping all side shoots – reduces yield the most in the first few harvests. Advantages are that this type of pruning is easily learned and taught, trees are uniformly controlled in size, usually no tying is required in the second growing season, and there are lots of secondary limbs to select from the following year. Drawbacks are that you guarantee the need for lots of thinning cuts at the second dormant pruning, you may need to loop tie the secondary branches in the second dormant season to prevent flopping during the third growing season.
Long pruning – selecting three primary scaffolds in the first dormant season but leaving them unheaded – is the other extreme. Small lateral fruitwood is left on the tree and some thinning may be done to select secondary branches. Similar light thinning is done in the second and third dormant seasons. Advantages are earlier production, far fewer thinning cuts in the second dormant season, and fewer watersprouts to remove. Disadvantages are that the method is harder to teach and more skill is required, there may be a need to tie vigorous trees in the second growing season to keep the primaries from flopping, trees are less uniform, and they may be more easily blown over during heavy storms.
Leaving trees totally unpruned is not recommended during the tree training years. Non-pruned trees may have heavier early yield in the third and fourth growing seasons but those are the lowest yield years in the orchards life. Eight or ten primary scaffolds will develop into a bushy dense tree that, long-term, is more subject to disease, blow over and limb breakage from poor branch attachments. If thinning cuts are made on these crowded primaries as the trees age, the remaining limbs result in an even less desirable tree.
Intermediate Pruning – The Best Compromise
The best compromise is intermediate pruning – selecting three primary scaffolds in the first dormant season, leaving on the tree small lateral twigs growing horizontally and non-vigorous lateral branches on the upper trunk or scaffold branches. The three primary scaffolds are tipped back lightly, usually to about 48-60 inches to where internodes are longer so that good secondary branching results. In the second dormant season, vigorous upright secondary branches are thinned out to no more than three on a primary while once again lateral fruitwood is kept. Disadvantages of this method are similar to long pruning: harder to teach and more tree variable. Advantages include less pruning needed to thin watersprouts in the second dormant season, less need to tie trees, less limb breakage and a fuller canopy compared to long pruned trees.
Early production in trial treatments using intermediate pruning is often very similar to production in the long-pruned trees. Keeping small lateral shoots and branches have several other benefits compared to short pruning. Their leaves shade the trunk and lower limbs and prevent sunburn. Sugars produced by these leaves nourishes the lower limbs and trunk and increases their strength. Finally these lateral branches are the first to spur up and produce crop.
Little additional training is needed in the third and fourth dormant seasons. Very few thinning cuts are made, only to maintain the dominance of the primary and secondary scaffolds. The third dormant pruning should be your final shot at correcting any mistakes made in previous years. Guard against limb breakage if there’s a heavy crop set in these first few years. To save bending secondary and tertiary scaffolds, it may be necessary to temporarily prop them up and secure them in the desired position with a loop of tree rope.
Twenty years ago many young orchards were pruned way more severely than necessary or desirable. Today, too often, little-to-no training is practiced with the mistaken assumption that yield will be the best with no downside. That is not the case. Good intermediate pruning will minimize blow overs while still returning reasonable early production and longer term tree health.