Pruning

Scaffolds

  • To get a tree that is well balanced, all of the scaffolds must develop evenly around the main stem, approximately 300 – 360 mm apart.
  • The scaffolds should be pruned back during the second, third and fourth seasons. Do not remove the primary bud so that the scaffold can continue growing upwards and outwards.
  • Only remove primary buds on the leader shoot in order to form scaffolds

Summer pruning

Before
After

Mechanical Pruning

  • Scaffolds must be pruned in summer by removing 100 – 200 mm growth. This will force a branch to develop numerous lateral branches that are able to bear fruit during the same year they were pruned in.
  • Summer pruning dwarfs a tree, and will considerably increase production during the first 10 years of a tree’s life.
  • Adult trees can be pruned after 10 to 15 years, especially if they start to crowd each other.
  • From the day it is planted, a young tree must be shaped.
  • Growth that follows pruning must be controlled.

Rejuvenation pruning

It is possible to stimulate declining production and nut quality in many of the older trees by pruning. The production of 1-2 years is lost by completely pruning back a tree,  but new growth and an increase in production and nut quality as a result of the pruning will compensate.

Growth regulants

A registered plant growth regulant will control excessive growth. When applying the substance, take care to follow the directions on the label strictly. If pruned trees are treated, use half the recommended concentration.

Pruning Mistakes

Sometimes it is necessary to prune a mature tree due to overhanging branches that get in the way of routine maintenance (i.e. irrigation, planting or mowing).  When the time comes to get out the Chainsaw, using proper techniques will prevent further problems.

These are 2 of the most common pruning mistakes:

  • In this particular case, a limb was pruned about 8 inches out from the branch collar. The branch collar is where the limb connects to the trunk.This is the natural area for a tree to grow over a pruning wound. In the photo you can see that the branch stub is rotting away.  You can also see that in an attempt to seal the wound, the tree has developed an exaggerated branch collar. If this branch had instead been pruned at the branch collar, the wound would have been sealed by now. Instead, the rotting branch stub has prevented proper wound healing and is allowing wood rotting fungi to penetrate into the heart of the trunk. Rule #1: don’t leave branch stubs when pruning.
  • The yellow arrow is pointing to a lower limb that has been pruned back at several places but still extends 10-12 feet from the trunk. By the missing bark on the limb near the trunk, it is evident that this limb is now dead and starting to decay. By hacking back a lower limb, one places the remaining limbs in the shade of upper limbs. Pecan Trees are shade intolerant, so if a limb does not received sufficient sunlight, the tree reacts by aborting the limb. The best course of action would be to remove lower limbs entirely, pruning the limb all the way back to the trunk and just outside the branch collar. Should the limb in the above photo not be pruned, it will probably end up being shaken off during harvest. Rule #2: prune lower limbs right back to the point where they are attached to another limb or the trunk.

Pruning of Pecan tree to promote new growth

Hedging Pecan Trees:

Mechanical hedging has become a standard practice among South-western US pecan growers. Trees are typically hedged (pruned on the sides of the trees) and topped mechanically. This operation keeps the tree size manageable, eliminating the need for removing trees, and it allows light to penetrate into the orchard, potentially increasing nut production on lower branches and in the tree interior. Hedging can reduce the amount of nut-bearing wood and therefore the fruit load, resulting in increased ‘on’ year nut quality. It can reduce ‘on ‘ year yield, increase ‘off’ year yield, and reduce alternate bearing intensity (Wood and Stahmann, 2004).

Although mechanical hedging has been widely adopted, there is no standard method of hedging. Individual growers each have somewhat different hedging practices. Reponses to hedging are likely dependent upon climatic conditions, variety, and orchard management. We are conducting a long-term field study to broaden our understanding of the effects of hedging on crop production and quality. In 2009, we began monitoring ‘Wichita’ trees planted in 1967 and spaced 30 feet apart in rows 60 feet apart, and ‘Western Schley’ trees planted in 1969, on 60′ x 60′ foot spacing. Both blocks are flood irrigated. The trees are hedged in the dormant season on a four-year cycle, in which every fourth row is pruned every fourth year (i.e. each row is pruned once in four years).

Starting prior to the 2006 growing season trees were side-hedged approximately 20 feet from the tree trunk, angled in at about a 50 angle. Western Schley trees are topped at 50 to 60 feet at the peak, and angled at 450. Wichita trees are topped at 50 feet. Each year we separately harvest rows of trees that were hedged

  • 1) in the previous winter [labelled ‘1st leaf],
  • 2) two winters prior [2nd leaf],
  • 3) three winters prior [3rd leaf], and
  • 4) four years prior [4th leaf].

Nuts are graded to separate marketable nuts, stick-tights, and pre-germinated nuts. Marketable nuts are weighed, shelled, and graded.

In both varieties, yields are reduced in the season following hedging. Western Schley yields increased approximately 1000 lb/a each year thereafter. The Wichita trees, on the other hand, rebounded somewhat more quickly from hedging and topping in the 2nd leaf (1200 lb/a more than 1st leaf). Third leaf yields were nearly the same as 2nd leaf; 4th leaf yields were about 700 Ib/a greater. In both varieties, kernel percentage was greatest in the season following hedging, and declined annually thereafter. Western kernel percentages over the four year cycle declined from 57.7% to 52.7% (almost 1.7% per year). Wichita declined from 62.8% to 60.1 % (about 0.7% per year). Nut size also declined with time after hedging. The size of Wichita nuts decreased from approximately 7.2 g/nut in 1st leaf to 6.5 g/nut in the 4th leaf. Western Schley nuts declined from 6.1 to 5.4 g/ nut. In both varieties, nut size declined more in the 4th leaf than in other years.

The number of stick-tights generally increased with time since hedging. Wichita had 1.3% stick-tights in the 1st leaf, which increased to 2.8% in the 4th leaf after hedging. In Western Schley the percentage of stick tights was 1.6% in the 1st and 2nd leaf, and increased to 2.3% in the 4th leaf after hedging. The amount of nuts showing pre-germination, or vivipary, varied from year to year, but apparently was not affected by hedging. In 2002 to 2006 to {hedging was initiated prior to the 2006 season} Western Schley trees exhibited a relatively uniform pattern of alternate bearing, with even numbered years being ‘off’ years, and the odd ones ‘on’ years. From 2007 to 2010, the alternate bearing pattern appears to have been considerably depressed. Wichita had a less pronounced alternate bearing pattern prior to the start of the hedging program, partly because of low yields in 2005, which should have been an ‘on’ year. Nonetheless, alternate bearing appears to be reduced since initiation of hedging. It is important to remember that the 2009 growing season was the first in which all four rows of the four-year pattern had been hedged. More seasons of data are needed to fully evaluate the effect of hedging on alternate bearing.

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