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Wednesday, June 20, 2018

Tree training starts with a successful graft

      When daily temperatures in June are above average, pecan trees seem to grow faster than normal. This is especially true for successful grafts. So I got up before sunrise to check my grafts during the cool morning hours. The first tree I came to was a bark graft applied to a young tree (photo at right). The scion has made impressive growth just 8 weeks since grafting.
     When I took a closer look at the scion, I found that there were 3 new shoots growing from original piece of scionwood (photo above). To encourage the development of a single central leader, I pruned off the upper two shoots and left the single lower shoot to become the new trunk.

       It is amazing how a single pruning cut can turn a pecan "bush" into a central leader tree. Establishing a central early in a new graft's life will help direct wood and stem growth into creating a strong new trunk.

    On the remaining single shoot, I noticed the growth and development of stalked buds (photo at left). Look carefully at the photo and notice the long leafless shoots that originate just above the rachis of each pecan leaf. To make sure I direct all new growth into and central leader, I pruned off every stalked bud on the tree. A more detailed description of the problem of stalked buds can be found HERE.
    Since this graft was growing so vigorously, I decided to cut off the grafting tape on the scion (photo at right).  At this time, I left the plastic bag and aluminum in place.  By cutting the tape off, I will prevent the possibility of the scion becoming girdled by the plastic ribbon.
     Before leaving this tree, I also took the time to remove any sprouts growing from the main trunk below the graft union. These shoots were so small and new, I just tore them off by hand (photo at left).
   

     To prevent the wind from breaking out my graft, I used some green flagging to tie the scion shoot to a bamboo training stick. This bamboo stake was taped to the tree with electrical tape back when the tree was first  grafted (photo at right).



    The next tree I came to was another bark graft placed on a much larger tree. In this case,  new shoots were growing everywhere and it was even hard to see the graft union (photo at right).

    I starting pruning this graft by removing all the trunk sprouts that had grown below the graft union. In the photo at right, you can see all the fresh pruning wounds I made by cutting off sprouts. Once cleaned up, the graft union is back in full sun and ready to promote the growth of the scion.
    Just like the previous graft, the scion had developed multiple new shoots. So my process was the same; Prune to a single shoot, remove stalked buds, and tie the new shoot to a training stick (photo above).


    On larger trees, I like to retain some lower limbs to help keep the root system supplied with the carbohydrates manufactured by leaves.  However, on this tree, one of the limbs I left was starting to compete with my graft for vertical supremacy (yellow arrow points to this limb in photo above). To promote my graft as the new central leader, I pruned off the upward growing limb while retaining outward growing limbs to provide important leaf area.