Wednesday, March 29, 2017

Sapsuckers have arrived

  Every spring, yellow-bellied sapsuckers stop to visit our pecan trees on their flight northwards. Long before the buds of pecan trees start to break, these members of the woodpecker family will drill a series of holes in the trunks of pecan trees (photo at right).  The holes are dug deep enough to allow rising sap within the tree' trunk to leak out. The sap provides nourishment for the birds as well as attracting insects to the sugar rich sap. When the sapsucker returns to it's freshly dug holes, the bird will dine on both sap and insects.
   Looking at the photo at right, you can see a row of freshly drilled holes in the bark. But six inches above that row is a row of old sapsucker holes that have been closed over by growing bark tissue.
   Sapsuckers holes may look bad but they do not damage nut production.

Monday, March 27, 2017

Counting pecan wood rings

    Whenever we remove trees during an orchard thinning process, I like to stop for a minute and look at the rings in the wood. Each year pecan trees lay down a new and unique layer of wood tissue. Take a closer look at the rings of a tree and you'll discover a little bit more about how a tree grows. During the spring flush of growth, new wood tissue is created with numerous large vessel cells (large pores in the spring wood pictured above). These large vessels are needed to transport the massive amounts of water and nutrients required to build the spring flush of leaves and new shoots. As shoot growth ceases by early summer, demand for water and nutrients slows and the tree creates wood tissue with only small vessels (summer wood pictured above). Small wood vessel cells may not be able to conduct large volumes of water but their small diameter makes it easier to move water up the trunk during the dry summer months.  

  The annual growth rings within a tree's trunk also offer a historical record of past growing conditions. The wider the growth ring and better that year was for tree diameter growth. The photo above shows the growth rings I found inside a Kanza tree we recently removed during a tree thinning operation. During the years 2014-2016 we experienced excellent weather for pecan tree growth--adequate rainfall and plenty of sunshine. The Kanza tree responded to these good growing conditions by at a creating wide, healthy growth rings.
    But look at the rings laid down during the dry years of 2011-2013. Wood growth during these hot dry seasons was stunted by poor growing conditions. In addition, the number of large vessel cells within these growth rings are severely limited (a response to drought). These large vessel cells are also stained dark brown (especially the 2013 wood). When a pecan tree suffers from drought, the large vessels stop working and the tree plugs up the non-functioning cells to preserve water within the tree.
    Next time you remove a pecan tree, take a little time to read the story left behind in the growth rings. I always seem to learn something new.   

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.