Friday, June 23, 2017

What happened to my pecan tree's central leader?

    When I drove by my pecan grove the other day, I noticed a tree with a branch that had broken out in the wind (photo at right). At first glance , it looked like the central leader had snapped and I lost the top of the tree. So, I got out my 8 foot tall orchard ladder to take a closer look and the make some pruning cuts.
   Once I climbed up the ladder I could get a good look at the branch structure of this tree (photo at left). To my surprise the broken branch was not the central leader. What was once the central leader was bent over under the weight of an excessively bushy top.
     My first step in pruning up this tree was to remove the broken limb (photo at right). Next I needed to straighten up the leader (red arrow). At the same time, I needed to thin out the number of limbs that branched out from the trunk at nearly the same spot on the trunk. Rather than attach a training stick to the tree, I decided to use a lower branch (yellow arrow) to help retrain the tree. I chose this limb because it was leaning out in the opposite direction of the leader.
     I held both these limbs upright and taped them together using electrical tape (photo at left). I now had my leader pointing in the right direction. However,  I also had a training branch pointing in the same direction and in direct competition with the leader.

    I pruned off the top of the training branch just above the electrical tape (photo at right). This pruning cut immediately gave a sunlight advantage to the leader. However, the training branch would soon sprout new shoots so,  I decided to try a little old fashion trickery.
   At the base of the training branch, I girdled the branch (photo at left). I removed the bark from the branch from the point the branch attaches to the trunk upward for about 3 inches. Girdling a branch will not kill it immediately but will inhibit the movement of nutrients into the branch and seriously hamper shoot re-sprouting. However, the wood in the girdled branch will remain strong enough to provide support for the leader. After a year's time, the leader should gain in diameter and strength and  I can cut out the girdled branch completely.
   Next I turned my attention to the leader.  Each spring, a pecan tree will sprout 3 to 5 new branches from the terminal portion of last year's growth. This forms a growth pattern commonly known as a "crows foot". The photo at right shows that the leader of this tree grew a crows foot in both 2016 and 2017 (red circles). This growth pattern produced such a mass of foliage that the leader became top heavy and bend over from the weight.
    To make sure the leader would develop into a strong, upright-growing trunk, I needed to prune off all the side branches in this portion of the tree.

   In pruning the top of this tree, I removed both the 2016 and 2017 crow's feet (photo at left).  Suddenly, I've reclaimed a single central leader.

    Once I got through with redefining the top of the tree, I turned my attention to the side branches. I found that the lateral branches had sprouted so many new shoots this past spring that I needed to prune off some excessive leaf weight. I did that by first removing any new shoots sprouting straight upwards from a lateral limb. Next I headed back any new lateral shoot that had grown more than 2 feet in length.
    My biggest problem in making these pruning cuts is that I needed my 8 foot orchard ladder for every cut.  I guess that is the price I pay for grafting onto a fairly large rootstock tree and witnessing 5-7 feet of new growth each year. 

    It took me about 15 minutes to prune my tree with a broken branch. It seems most of my time was spent moving the ladder and climbing up and down. This fall (late Oct.) I'll prune out my training branch.