Tuesday, March 12, 2013

Trimming last year's bark graft

    Last summer I top-worked a pecan tree using a bark graft and I showed you every step I took from placing the graft to mid-summer tree training. You can review those steps by clicking on the following posts.

1. Top working with a bark graft
2. Bark graft bursting
3. Training a new bark graft
4. Summer training a bark graft
5. Painting a bark graft

   Since only fresh air could cure my cabin fever,  I decided to go out this afternoon and show you how I  make some important trimming cuts on one-year-old bark grafts.
    My first step is to use a knife to peel into the bark of the stock on the opposite side of the trunk from the scion (photo at left). This gives me some idea how far the stock has died back. The green and cream-colored area is live bark. The cinnamon-colored area is dead tissue. This bark graft is somewhat unusual in that the bark didn't die back farther down the stem. In any case, I now know where I can make an angled cut on the stock to speed the healing over process.
    I like to cut the stock off on least a 30 degree angle (photo at right). This cut will help the tree callus over the wound much faster and will help build a stronger graft union. If  the bark had died back farther down the stock, I would trimmed the tree at a steeper angle to remove all the dead tissue on the top of the stock. With the size of the root system under this tree, I wouldn't be surprised to see this graft healed over by the end of the summer.
    The graft is not the only part of this tree that needs trimming. As you can see in the photo at left, I always like to leave some nurse limbs on a top-worked the tree to help feed the root system with leaf-manufactured carbohydrates. However, you can also see that several of these side limbs have produced shoots that are growing straight up toward the sun (photo at left). These shoots need to be pruned off to help focus all the tree's energy on pushing the new graft.
    I removed about one third of the shoots on the side branches (photo at right). In making my pruning cuts, I concentrated on removing upward growing shoots leaving shoots that where growing laterally. With less direct competition, this graft is now ready to grow vigorously when spring arrives.