Checking last year's grafts

     Last winter was rough on new grafts. Like area many growers, I've discovered that some grafts made in 2013 were  completely dead all the way down below the graft union. Other grafts looked perfectly OK and were sprouting new shoots. The most interesting part of part about graft winter kill this year is that it had nothing to do with choice of scion cultivar.  In fact, I can find no logical reason why some grafts died over the winter whiles other thrived.
    The photo above shows two Kanza grafts made in the same field just 100 feet apart. The graft on the left is completely dead. You can see where I had tied the graft's new growth to a bamboo stake with blue fagging tape last summer. Now, the tree is pushing out trunk sprouts below the graft union in an effort to grow a new top. Note the reddish color of the foliage. This tells me that all new shoots are coming from the seedling rootstock. I'll let this tree grow out this year and place another Kanza scion on the tree in 2015.
   The healthy tree (above, right) has already developed numerous new Kanza shoots. The only problem is that this tree has developed a 'lolly-pop' appearance--all the new shoots are clustered at the top of last summers new growth. This growth pattern is common for open grown pecan trees and is one of the major causes of poor tree structure. During this time of year I like to practice a little directive pruning and follow the 2-foot rule for tree training.

    The photo at right shows before and after views of the upper portion of last year's healthy graft.  There were at least eight new shoots growing to form the 'lolly-pop' at the top of this tree. My first priority was to identify the one vigorous shoot that would become my central leader. Next I removed all other lateral shoots within 2 feet of the top of my chosen leader.  This left me with a couple of lateral shoots at the base of the 'lolly-pop'. I then pinched out the growing points of the two lateral branches to slow their growth and help focus more  of the tree's energy on the central leader.
    Pruning out most of the 'lolly-pop' will also help stimulate growth from lateral buds further down the stem. In a couple of weeks, I should see buds breaking all along the trunk in areas that currently look bare. In training a young tree, my aim is to develop a well balanced tree with lateral branches growing out at regular intervals all along the trunk.   

Pecan grafts breaking bud

   Its been about 3 weeks since I grafted pecan trees in my orchard. Look carefully at the photo at right and you'll notice that the buds on the scion have broken and are about one-inch green. Below the graft union is a profusion of trunk sprouts, producing leaves with the characteristically red tinge of a seedling rootstock. You should also note how the trunk sprouts got a head start on the scion sprouts in terms of growth.  When I applied the graft, buds on the scion were fully dormant. In contrast, buds on the trunk had already acclimated to spring time temperatures and were primed to go as soon I cut the top and placed the graft.

   To focus all the tree's energy into growing the buds on the scion, I pruned all the trunk sprouts off this tree. I like to complete this simple task as soon as I see new growth on the scion.  I have seen cases where trunk sprouts were not pruned off during the first summer after grafting and those sprouts eventually out-grew and shaded-out the scion. Lost in the deep shade of trunk suckers, a sprouted scion will actually die from lack of sunlight.
   The lesson here is to check your grafts early and often. And don't forget to always carry a pair of pruning shears.

    The photo at right shows a little larger tree with another graft I made this spring. The graft has sprouted but the side limbs I left below the graft have grown even faster. I left these lowers limbs on the tree to provide leaf area to support the root system but you can already see that these side shoots have turned to grow upwards and are competing with the graft for sunlight. I don't want to remove all the leaves below the graft union but I need to slow down the growth of these lower limbs. 

   The photo at right shows the same tree after I made several pruning cuts. First, I pruned off all but two branches below the graft. Second, I  removed all upward growing shoots from those two branches. And finally, I pinched back the terminals of edge side branch making sure to prune to an outward growing bud. Now my graft is back in full sun and ready to take off. I'll be back in a couple of weeks with some plastic tape to tie the scion's new growth to my bird perch. Oh, how I would hate to see a successful graft blow out in the wind!

Winter kill of pecan trees

    Although the winter of 2013-2014 didn't set any records for low temperatures in our area, we did drop down to cold enough temperatures to cause some obvious winter kill. The photo at right shows two Shoshoni trees. The tree on the left has leaved out normally while the tree on the right has only few new shoots growing  on the lower trunk and a few low branches (see close up photo below). This mostly dead Shoshoni tree is a perfect example of an alternate-bearing cultivar that lost winter cold-hardiness following an "on" crop year. A heavy crop pulls massive amounts of plant nutrients out of tree stems in an effort to fill nut kernel. The following winter, depleted branches are less able to withstand cold winter temperatures. Following a heavy crop, cold damage can occur even at moderately cold temperatures (<-10 F).

   The photo at left shows the few green shoots produced by our heavily damaged Shoshoni tree. With the massive amounts of limb loss sustained by this tree it would take 5-7 years for this tree to recover its canopy. In the past, Shoshoni has proven to be a difficult cultivar to manage and trying to help this tree recover is probably not worth the effort. We'll be making only one more pruning cut on this tree--at ground level!

    I've seen one other type of cold injury this Spring. Again the damage occurred on the cultivar, Shoshoni, but this time the damage is not crop load related. The photo at right shows a Shoshoni tree with several large limbs killed by winter cold. It wasn't until I closely inspected the structure of this tree that I discover why only a portion of the tree's canopy was killed during the winter.

 The photo at left reveals that this Shoshoni tree suffered major limb loss during the ice storm of December 2007. Broken limbs were pruned off leaving large branch stubs. New shoots then sprouted out from these branch stubs and grew at an extremely rapid rate. Rapidly growing shoots remain active and full of sap late into the fall. This delay in the normal hardening-off process before the start of winter only leads to a reduction in cold hardiness. The side of this Shoshoni tree that did not break in the ice storm, suffered no winter injury.
  We will be pruning the dead limbs out of this tree. After pruning, this tree will have enough canopy left to support a partial nut crop this fall.

Another sawfly species appears

  As this year's dry spring weather continues, another species of sawfly larvae has appeared in our pecan grove. Megaxyela major produces a yellow larvae with black head and a row of black spots on each body segment (photo at right). These sawfly larvae chew large holes in the foliage and can usually be found curled around leaves, rachises, or leaf midribs.

    Like the sawfly species I described in early May, this species of sawfly has a single generation per year. Fortunately, I have never seen M. major populations so large as they require a pesticide application. The cluster of sawfly larvae pictured at left occurred on a single pecan branch terminal. It has been the only colony of his species of sawfly we have found across our entire 80 acre pecan  grove.