Wednesday, June 15, 2016

Training new pecan grafts

     I set on a lot of bark grafts this year and the scions are growing like mad (photo at right). So far this year, I've already made one pass through the orchard to prune off trunk sprouts in and effort to force new growth on the scions. Now with plenty of new shoot growth, its time to select my new central leader and prune the scion down to one shoot.
   Two buds have grown from the scion, both creating strong shoots (photo at left). To develop a tree with a single central leader, I'll need to prune off one of these two shoots. Some growers like to leave multiple scion shoots on the tree all summer long. Then, late next winter, they will prune the scion down to one shoot and harvest the extra shoots for scionwood. I like to make the choice for a new central leader as soon as possible. Pruning down to one shoot in mid-June gives me the entire summer to grow a strong and dominate central leader.

    With a single cut, I made my selection for a central leader (photo at right).  When choosing which shoot to save, I choose to keep the strongest growing shoot.  About 80% of the time, the strongest shoot will arise from the lowest bud on the scion.

    Its amazing to see how much a scion can grow in diameter in just a few short weeks. After trimming the scion down to one shoot, I noticed how much strain the green grafting tape tied around the scion was under. To relieve the girdling pressure of the tape, I used my knife to cut off the tape, while leaving the rest of the graft wraps in place (photo at left).
    When making a bark graft, I often leave a nurse limb on the tree under the graft to help provide photosynthetic energy to the root system. But when leaving a nurse limb on the tree, I also make sure that upright sprouts don't develop along that limb that could compete with the graft. In the photo at right, I've used red arrows to point out several upright sprouts that have developed on my nurse limb. Once these shoots are removed, the graft will continue to grow without any direct competition.

   The new scion shoot on this graft is growing so rapidly that it already developed stalked buds (photo at left). I used my fingers to grab these elongated buds and pulled them off the tree.  Not surprisingly, I found stalked buds at every node on the new shoot, from the very base of the shoot to the apex. I removed them all.

     On another graft, I found the new scion shoot had terminated with a flower cluster (photo at right). In this case, I pinched off the flower cluster and left the adjacent stalked bud in place (red arrow). This elongated apical bud will become the primary growing point for the scion's central leader. The stalked bud I left in place will quickly resume extension growth originally stalled by the formation of pistillate flowers.