Monday, July 8, 2013

Poor tree growth and the appearance of stump strouts

        The past couple of summers have been hard on young pecan trees growing in the Midwest. The heat and drought have been brutal. This spring I have seen several young trees produce only a smattering of new leaves on upper branches while sending up vigorous stump sprouts from below the soil surface (photo at right).  The stump sprouts on this tree first developed in 2012 and have continued to grow this year. 

   This year's new shoots are only one-inch in length on the upper portion of the tree (photo at left). The leaves are small and have several missing leaflets. The tree just looks sick!

      At the base of the tree, the bark on the main stem is sloughing off (photo at right). To me, this indicates that the conductive tissues (xylem and phloem) in the stem have been damaged, interrupting the normal flow of water and nutrients.  Its no wonder the top growth on this tree is so anemic.
   The growth of stump sprouts is the tree's way of replacing the damaged portion of the tree with healthy stems that support large, healthy leaves.

    One way to deal with this situation is to coppice the tree (photo at left). It was obvious to me that I was going to lose the original portion of this tree. The growth I found on the upper branches was just too sparse to keep the tree going. On the other hand, one of the stump sprouts had already grown 5 feet tall in two years time.  I simply used my chainsaw to cut down the original trunk and the smaller stump sprouts at ground level.  My tree might have a much smaller top after coppicing but the potential for new growth is much better.
    This tree is a seedling growing in our pecan breeding plots and will remain a seedling in the future. If you need to coppice a grafted tree, plan to re-graft the tree in a year or two.  

    The stump sprout I saved had three equally vigorous shoots growing near the top of the tree. To shape this tree into the central leader form, I tipped back the two side shoots to outward growing buds and left the central shoot free to grow into a strong leader (photos at right). I'll need to watch this tree carefully this summer. There is a lot of root energy pushing the new top growth and that will require plenty of return visits for additional summer pruning.