Written By Brent Holtz, UCCE Madera County Farm Advisor
Pruning after the first growing season is critical in determining the shape and performance of an almond tree. At this time you should select three permanent primary scaffolds that will form the framework of the tree. I have seen quite a few first year trees pruned improperly in Madera County, resulting in premature loss of tree vigor, increased susceptibility to disease, and in some extreme cases the eventual removal of orchards; all because these trees were pruned improperly their first dormant season.
The primary goal of the first dormant pruning is to select three primary branches with as much space as possible between them (fig. 1-A). Wide spacing ensures the best chance of a strong branch attachment that will not split as the tree matures. The three primary scaffolds should be oriented 120 degrees apart when viewed from above (fig. 1-B). Such an arrangement reduces the chance of splitting branches, leaning trunks, and crossing limbs. If possible, one of the three primary scaffolds, preferably the strongest, should grow into the prevailing wind, usually northwest. A strong, vigorous limb on the north side helps keep the tree from being dominated by growth on the sunny south side of the tree.
Pruners should also pay attention to the angle of the primary limbs when selecting them; for the scaffold angle determines whether bark will become embedded between limb and trunk. The ideal primary scaffold grows 45 degrees from the vertical and the horizontal (fig. 1-C). If the ideal limb is not present try to find limbs at least 30 degrees from the vertical or at least 30 degrees from the horizontal. Limbs that grow at too flat an angle tend to lose their vigor and upright orientation. Limbs where the bark becomes embedded will be weak and may split with the first heavy crop.
Why only three primary limbs? No tree needs to have more than three primary limbs. A mature tree with more than three limbs will limit access to limb-shaking equipment. I have seen a few prime orchards in Madera County decline prematurely because they were too large to trunk shake, but because they had more than 3 primary limbs they could not be limb shaken and thus the trees were barked severely while attempting to trunk shake these large trees. Because of tree barking almost every tree had Ceratocystis bark canker, so instead of reaching optimal age and production these orchards were being removed.
What if you can’t find three acceptable primary scaffolds? Selecting two sound scaffolds is better than keeping four poor ones (somebody will probably argue with me here)! After the primary scaffolds have been selected, the next step is to remove all other major limbs that originate from the trunk, and all growth below the lowest primary limb. Pruners should leave small lateral branches on the primaries; this growth promotes scaffold caliper growth and is the first to develop spurs and produce nuts.
Growers can use three methods for pruning the first growing season: short pruning, long pruning, and intermediate pruning. These tree pruning methods do not affect trunk diameter or limb caliper; but production differences related to tree training occur the first few harvests but disappear after trees mature. In choosing the pruning method a grower must decide which is more important, high early production or ease of training during the early growing years, and the grower must also consider the growth habit of the variety and the wind conditions in the orchard. I usually prefer the happy medium-intermediate pruning.
Growers who use long pruning make no major heading cuts on primary on primary scaffolds and retain small lateral branches that will provide leaf surface and early fruiting. This type of pruning allows the tree to develop a natural branching habit. Scaffolds and fruit wood develop quickly, and the canopy, because it is relatively uncontrolled, grows rangy. Long-pruned trees usually need roping or tying (fig. 2-B). Even after being properly tied, limbs may break. If ropes are used, they must be placed as high on the primary scaffolds as possible so that the scaffolds do not bend over them. In this system secondary and tertiary branches are selected from the natural branching of the tree. Long pruning takes time and judgment, and if the pruner is uncomfortable with making second and third level framework decisions, another pruning method other than long pruning may be more appropriate. The main advantage of long pruning is heavy early production. Disadvantages include the need for more work and care the second growing season and greater difficulty in achieving an ideally shaped tree. Willowy growing varieties such as Monterey may be unsuitable for this system of training.
This type of pruning involves heading each of the three primaries back to 18 -24 inches. Unfortunately I have seen some pruners in Madera County head their primaries back to 12 inches or less–this is much to severe and will lead to “elbow” growths and sharp secondary angle branching. Short pruning done properly (18- 24 inches) stimulates vigorous secondary growth that is largely removed later with thinning cuts. This type of pruning allows growers a large role in shaping trees, because the vigorous regrowth provides many choices for secondary limb selection where you want it. Because short-pruned trees are short in stature, they rarely require roping or tying (fig. 2-D). Keeping trees short is particularly advantageous during the second growing season in areas with strong wind in April and May. Also, in the case of weak trees, short pruning can be a desirable way to stimulate vigorous shoots the next growing season. Although this is an easy pruning method, growers must consider the trade-offs. Heading cuts on vigorous trees can encourage vegetative growth at the expense of early nut production. On short-pruned trees, developing a primary scaffold long enough to limbshake can be difficult.
A compromise between short and long pruning, intermediate pruning contains elements of both. Growers make heading cuts high on the primary scaffolds. These cuts are at 42-48 inches from the trunk, usually at a point just below the closely spaced buds that are common in the last 6 to 12 inches of shoot growth (fig. 2-C). Heading at this distance greatly reduces the number of new shoots that originate near the end of the branch in the second leaf. This reduces the shoot weight at the end of the primary scaffold and makes it less likely to bend in spring winds. As with long pruning, orchardists who practice intermediate pruning keep small lateral branches for their leaf surface and to promote early fruiting. This system of pruning generates fewer undesirable water sprouts than short pruning, but it requires thought when selecting among the relatively few secondary branches in the second dormant season. If intermediate pruned trees are especially vigorous or if the variety is willowy, branches may require roping prior to the second leaf. Overall, this is a successful training system that avoids the worse problems of long pruning but offers advantages in terms of early production.
Second Dormant Pruning
After the second growing season the grower selects the secondary scaffolds–two per each primary limb. A secondary scaffold is a vigorous, upright lateral that forms a “Y” off a primary limb. The secondary branches should be evenly spaced around the canopy (6 branches, 60 degrees apart) and have an upward and outward orientation. The secondaries do not need to be headed unless excessively long, since most almond trees branch sufficiently without heading cuts. Other than pruning limbs that compete with the selected secondaries, removing badly crossing branches, and cutting an excess of internal water sprouts, additional limb removal is usually unnecessary.