Wednesday, March 22, 2017

Pecan trees still waiting for Spring

    With temperatures hitting the 80's (>27 C) a few days ago, everyone is talking about Spring arriving early this year. So today, I went out to the pecan grove to see if I could find any signs of bud growth on our trees. The vast majority of pecan cultivars I inspected were still fully dormant. The Pawnee and Posey twigs pictured above are just two examples of cultivars with dormant buds. On the other hand, Mohawk buds have started to split open the outer bud scale (crack in the scale marked by red arrow). To get a closer look at the Mohawk bud click on the photo for a full screen photo.
   Outer scale split is the very first indication of pecan bud swell. It also marks the time when pecan roots start their spring flush of new growth. In just a couple of weeks we should see all pecan cultivars start bud expansion. In five weeks time, I'll be grafting trees.

Monday, March 13, 2017

Narrow crotch tear-out

     The other day, I spotted a young tree in my orchard with a wind-torn branch (photo at right). At first, all I was thinking was, "how did that happen?". But then, as I approached the tree, I immediately recognized the cause of the break--a narrow  crotch up in the center of the tree that I somehow missed during earlier pruning trips through the orchard. Just a month ago, I wrote about the importance of pruning out narrow "V" crotches to ensure that limbs don't tear out during wind storms. I guess its time to go back through the orchard again to make sure I didn't miss other narrow crotches.
    A closer look at the damage reveals that the tree basically split in two, right down the center of the tree (photo at left). At the top of the wound, you can see a bark inclusion that forms between the two halves of a narrow crotch. Under the pressure of strong winds, narrow crotch split apart and then one side ripped down the trunk for about 12 inches.
   I pruned off the bent and fractured limb and I left what was left of the central leader in place. Sometime before this tree breaks bud and grows a new crop of leaves, I'll need to place a brace up in the tree to prevent the weakened central leader from breaking over. I'll attach the brace to the tree using duct tape and keep the brace in place until the central leader grows enough wood to support itself (probably 2 years for this size tree).

Wednesday, March 8, 2017

Spreading fertilizer on the pecan grove

   With rain predicted at the end of the week, we decided to spread a little fertilizer on our pecan grove today. We spread 150 lbs. of urea (69 lbs nitrogen) and 100 lbs. potash (60 lbs. potassium) on each acre of our orchard. With this volume of fertilizer, its going to take us a little while to cover the entire Experiment Field.
   Today's fertilizer application is the first part of our regular fertilizer program. We apply fertilizer twice per year every year. During early March we spread nitrogen and potassium. Then, in October, we'll make an additional application of nitrogen. In total, we are adding 115 lbs of nitrogen and 60 lbs of potassium to our trees annually.

Thursday, March 2, 2017

Anatomy of the branch collar

   Every time I talk about pruning off low limbs from pecan trees, I end up describing how to make the proper pruning cut. Typically, I've talked about removing a limb by cutting just outside the branch collar (photo at right). Removing limb in this manner promotes quick healing, reducing the spread of wood rotting organisms. But is there an anatomical reason this pruning method works so well? Let's look under the bark to see.

    Last summer I cut a pecan sampling and carefully pealed the bark off the main stem and all the side branches (photo at left). After drying, the patterns of wood grain formation really became pronounced. You can see a raised branch collar formed by wood fibers that flow vertically around the side limb. By cutting limbs off outside this collar you don't disrupt the flow of water and nutrients from the roots to the upper portions of the tree. Cutting into the collar causes a disruption to sap flow and  creates a wound that takes much longer to heal.