Training and pruning almond trees is considered an art and a science by many growers. The art is the pleasant tree shape created by the skills of the pruner and the science is the tree responds to pruning. Both art and science interrelate to each other. To create a well formed tree the pruner needs to understand tree responses to a given pruning cut. In addition, the pruner needs to understand that the purpose of pruning is to train a young tree to a permanent framework which will optimize a bearing surface as soon as possible. Furthermore, he needs to understand that it is counterproductive to be fighting the tree's natural growth habit.
There are basic principals and guidelines that apply to the formulation of almond trees. Some will be discussed in this article but first let's consider “What is pruning?” Pruning is the removal of unwanted growth (shoots, limbs and branches) and consequently the removal of leaf surface which dwarfs tree development.
The first pruning is done soon after the trees are planted, their tops are cut at 42 inches from the ground. This will allow the development of a high head. For some time, many orchards have been developed with a high head without any problems with the wind. A high head makes the tree trunk quite visible when trees are mechanically harvested. Also, it will provide more room for primary scaffold selection in the first dormant season.
Top eight inches
When the new shoots have grown four to six inches long in March — April, eliminate all of them below eight inches from the top. This is to say, the top eight inches will retain its shoots. Examine these shoots and where there are twins, eliminate the weaker one. The elimination of unwanted shoots early in the season will not decrease tree development due to reduced leaf surface.
The primary scaffold selection is done after the first growing season. At this time upright branches with wide angles should be selected because they are stronger than branches with narrow angles. The recommended number of primary scaffolds is three or four. In some orchards however, up to seven primary scaffolds have been selected without any problems. If multiple primary scaffolds are selected, they should be distributed up — down and around the trunk. All horizontal and narrow angle limbs should be eliminated. The elimination of these limbs will create more space for the selected limbs.
After the pruning is done, the tree canopy should be well balanced without open spaces. Then, the trees should be tied and its main scaffolds headed.
The tying can be done in the winter or early spring. The heading of scaffolds can be done in the winter but at this time pruning cuts invigorate limbs. The best time to do a heading cut is when the apical bud begins to leaf out. At this time, heading cuts promote lateral shoot growth. A heading cut is done to eliminate the short lateral growth on the top of the scaffolds. Also, it is done to have all the limbs at the same height.
After the second growing season, the second dormant pruning is done. Low limbs that may interfere with herbicide sprays or mini-sprinkler irrigation should be eliminated. The center of the tree should be kept moderately open to allow light penetration inside the tree. This is done by eliminating limbs and vigorous shoots growing through the center. Secondary limbs with narrow angles should be eliminated at this pruning.
Once the pruning is done, the trees should be tied with a flat rope. This tie should be placed 24 inches below the top of the tree. This tying keeps the tree upright thus avoiding the umbrella shaped trees. The tying should be done in the winter. Once the tree begins to grow and fruit set has taken place, it is very difficult to tie trees.
The third dormant pruning is done after the third growing season. This pruning consists of cutting off limbs from the north side of the tree growing towards the south. The purpose of this pruning is to keep the south side of the trees upright and the north side growing towards the north.
Restricting the pruning to minimum, in the second and third year, minimizes the number of water sprouts produced in the third and fourth year. Therefore, to eliminate the need to prune off water sprouts in the fourth year, the pruning must be kept to a minimum. Most varieties require tying beyond the fourth year. In fact Nonpareil and Monterey require tying up to the eighth and 10th year.
No yield increases
Pruning doesn't increase yields in young or mature orchards. In fact, when young trees are pruned too much, the yields go down. This has been demonstrated in experiments conducted in Kern County. Therefore, the reason for pruning is not related to yield increases but it is related to other management practices. The reason to prune a mature orchard should be based on insect management practices, market strategies and sanitation practices.
When mature almond orchards get to be higher than 20 feet, it is very difficult to remove all the mummies in the winter. If a grower is having high reject levels from a mature orchard whose trees are higher than 20 feet, he needs to lower the tree height using a tower pruner. Pruning is also necessary when the crop is not drying on the orchard floor due to lack of sunlight. A prolonged drying period on the orchard floor can result in a high ant damage.
The in-shell market doesn't allow hull-tights (stick-tights). Therefore, to have more than 90 percent of the nuts completely open, the sun must penetrate well throughout the tree canopy. This is accomplished by having the trees well pruned.
Pruning is also justified when there is the need to remove broken branches or branches that have died due to Ceratocystis Canker.