Tuesday, June 30, 2015

Trimming up a bark graft placed on a stump sprout

   A couple of years ago we cut down several trees in our pecan scionwood orchard to make room for some new cultivars. Our idea was to cut a tree at ground level, allow it send up stump sprouts, thin the sprouts down to one strong-growing shoot, then graft that shoot the following year. The photo at right shows you one of the grafts I  made on a stump sprout this past spring. One one downsides about grafting a stump sprout is that for several years the tree will continue sending up new sprouts all around the outside of the stump. In the photo a profusion new shoots has grown around the base of my graft.
   The first thing I did was the break out my gas powered weed trimmer and carefully cut off all the new stump sprouts at ground level. You need to have a steady hand and a good eye to make sure you cut just unwanted sprouts and not injure the bark of the stem you are saving. Of course you can use hand clippers to do the same job, but I have found that a good strong string in my weed trimmer actually does a better job of cutting new shoots off at ground level or even a little below.
    The photo at left shows the tree once all the stump sprouts have been removed.

     After trimming off all sprouts that were growing on the trunk below the graft, I turned my attention to the graft itself (photo at right). On this graft, three shoots have developed from the scion. One shoot grew from the upper scion bud while two shoots developed from the lower scion bud. At this time of year I like to choose a single shoot growing from the scion to become my new central leader.
    I first looked at the shoot growing from the upper scion bud (photo at left). This shoot had a very confused growth pattern and was cover with long lateral shoots developed from the growth of stalked buds. This shoot looked like it would be difficult to train so I  decided to prune this shoot off immediately.

   After pruning the scion back to the two  lower shoots (photo at right). I could see that either one of these shoots would make a good central leader. The shoot on the left had a slightly larger diameter so I chose to make it my new central leader while pruning out the other.

    When you graft onto a stump sprout there is a lot of root energy pushing the graft to grow extremely fast. As a result the tree will develop stalked buds a every leaf axil (photo at left). Now that I had pruned the tree down to a single shoot, I carefully pulled off every stalked bud.

   Once I completed all the pruning, I used flagging tape to tie the shoot to my bamboo stake (photo at right). I also cut off the small piece of grafting tape that held the plastic bag tightly around the scion. I don't want any possibility of girdling such a fast growing graft.
   My final step was to replace the deer cage over the graft to prevent browsing injury.