Introduction by Jerry, Henkin, NNGA Librarian
“Pruning Nut Trees for Production” by J. Benton Story was written 35 years ago, but the advice on pruning is still valid today. Though the article was written about pruning pecan trees, it applies to any of the nut genera grown in the U.S. and Canada that require a straight, single trunk. And aside from the areas in the southeastern U.S., where the weather has already reached the high 70’s, nut trees can still be pruned in March, before the tree sap starts to run.
Pruning Nut Trees for Production*
By J. Benton Storey, Department of Horticultural Science, Texas A&M University, College Station Texas
The central leader training system is far more advantageous for pecan trees than old systems that may have been used for hand harvest. Now that mechanical harvesting is essential the central leader offers a much better balanced tree on which the vibrations created by the shaker will be most effective.
A central leader training system increases the effective number of trees per acre. It allows maximum leaf exposure per acre which increases the productive capacity of the orchard. Trees trained to a central leader system develop a productive “skirt” along the side and lower portion of the tree. Crowding can occur in ultra-high-density orchards as early as the ninth and tenth seasons. As these trees crowd the lower skirt is lost and production drops. Once the fruiting wood on the side of a tree is lost, it is very difficult to restore production in this section of the tree, even with alternate tree removal.
A central leader is forced by proper pruning at planting time. One half of the above ground portion of a young tree must be cut back. When growth begins, select one strong shoot for the central leader. The central leader is cut back the first, second, and third dormant season to continue to force strong shoot growth at the top of the tree. One shoot is selected in June as the central leader. Extensive side shoots will develop, whose purpose it is to manufacture photosynthates for central leader extension, sun protection, and girth development.
Lateral shoots are “pinched” to prevent them from developing into major branches. Pinching should be accomplished during the first and second growing season by removing the soft light green growing point of the lateral shoots. The growing point can be easily broken off with the fingers. Each lateral shoot should be allowed to grow approximately 12-24 inches before the growing point is pinched out. Leaves on the lateral shoots will expand to an extremely large size. These leaves will produce photosynthates for rapid central leader expansion and terminal growth. It I not unusual for the central leader to grow 36 inches the first season.
Tip-pruning should be practiced on permanent limbs by removing 3 inches of terminal growth in the months of January and February. Only shoots should be tip0oruned that are 32 inches or longer. This practice stimulates the development of numerous small lateral shoots.
These shoots are capable of producing pecans earlier than non-tip-pruned shoots. Tip-pruning will bring small trees into commercial production at an earlier age and encourage stronger central leader development. Tip-pruning will also reduce tree size during the first ten years. Trees should be top-pruned between the 3rd and 5th years. It is not needed on older bearing trees.
During the establishment of an orchard undesirable limbs develop during the 4th to 7th years which must be removed.
“Y” crotches or two central leaders should not be allowed to develop. If two upright trunks of equal size develop, one must be removed entirely. This should be done as early in the life of the tree as possible. It should not be put off, hoping that the problem will correct itself. This pruning can be practiced any month of the year. Pruning the first three years with careful central leader selection significantly reduces the probability of “Y” trunk development.
Frequently 4,5, or 6 shoots develop at the end of a young limb creating a crow’s foot arrangement. This often happens when the trees are growing rapidly and several buds force at the same time before any one is able to become dominant. These shoots should be thinned out so that only 3 shoots result. This is best practiced in January or February the 5th or 7th year. If tip-tip pruning is practiced, the crow’s foot problem is greatly reduced.
*74th Annual Report of the Northern Nut Growers Association, 74:235 – 236 (August,1983)