Wednesday, June 6, 2012

Training a new bark graft

    Back in April, I used a bark graft to top work this tree (photo at right). By the first part of May, the scion had broken bud and began rapid growth.  Now in June, the scion's new growth is nearly 3 feet in length and its time to start the tree training process.
     I began working on this graft by removing all suckers sprouting from the trunk below the graft. I next removed the bird perch and cut off the grafting tape that sealed the plastic bag around the scion (photo at below). With the extraordinary growth rate this graft has already demonstrated, it is extremely important to make sure the scion doesn't become girdled by green tape.
   You can see that I have 4 strong shoots growing from the scion. As usual, the bud closest to the graft union received the biggest push from the stock. In this case, both primary and secondary buds at the base of the scion produced new shoots (lower left side of the scion) diluting to energy that could have been directed to a single bud. Regardless, my job is to pick the strongest shoot to become my new central leader and remove all others. 
    The uppermost bud had produced the largest shoot on the scion and is my choice to save for the new central leader. I removed the lower 3 shoots and pruned off the small stub at the top of the scion (photo at right). 
   Pruning to a central leader at this point will force the scion to grow even more rapidly. To prevent the wind from breaking out the new growth, I attached a eight foot long piece of 1 x 2 inch board to the side of the tree with duct tape (photo at left).  I then used one inch wide flagging tape (white) to tie the new shoot to the board. As the shoot continues to grow upwards, I'll tie the shoot in several places further up on the board.
    Before leaving this tree, I decided to prune a portion of the original tree back.  I concentrated on removing limbs and shoots that were pointing upwards and competing with the scion for sunlight. I removed one entire branch all the way back to the trunk, the pruned off several upward growing side shoots. You can see in the photo at right that the scion is now receiving full sunlight. 
    All summer long I will be using directive pruning techniques to ensure the formation of a strong trunk. By the end of the growing season, I fully expect this new graft to grow at least 7 feet in height and 1.5 inches in diameter. But, it will only grow that large in I keep the graft tied to the stake and competing limbs pruned off.