Thursday, May 26, 2022

Directive pruning last year's grafts


      Once I finish up grafting for this year, I turn my attention to pruning last year's successful grafts. The photo at right illustrates the typical appearance of a young grafted tree in its second leaf. Last year, I carefully pruned the graft to ensure a single, strong central leader. But this spring, the tree popped multiple new shoots from the terminal of last year's growth.  If allowed to remain for the rest of this summer, these multiple shoots will create what is commonly known as a crow's foot and I will have lost my central leader. That is why I'm such a strong proponent of directive pruning. By pruning during the period of active shoot grow, I can "direct" the tree's new growth into maintaining a single leader.

   The photos above shows the terminal of my young grafted tree. Three shoots have developed at the very top of the tree. I identify the strongest growing shoot among the three and then prune out the others.

     To help focus the tree's growth energy into my new central leader, I also remove all lateral branches that arise from the main stem within the top 2 feet of the tree (measuring from the top of this year's new shoot growth). (photo above)

     Since I still have the bamboo stake in place from last year, I tied the tree upright to encourage to formation of a straight tree trunk. Later this summer, I'll probably replace the bamboo with a longer (and stronger) tree stake that will help me keep this tree growing the way I want. I allow lateral branches to develop lower down on trunk (but above the graft union). Lateral branches will increase tree leaf area helping to capture more sunlight to produce the carbohydrates needed to sustain rapid tree growth. These lateral limbs also catch more wind which in turn promotes trunk diameter growth.

    The photo at right is another example of a graft in its second leaf. In the past, I've called these trees "lolly-pop" trees because of the ball of new growth at the top of the tree. This tree also needs directive pruning.

     Whenever I go to prune a young tree, I always start at the top and work my way down. In this example, I have three shoots growing at the terminal but it appears I already have a strong central shoot. However, to reinforce the dominance of this new central leader, I'll prune off all competitors. Again, I stick to the 2 foot rule--No lateral branches within the top 2 feet of the central leader.

    Once I finished pruning I noticed that I already had a couple of lateral buds breaking further down on the stem (photo at right). I make sure I leave these in place for now. 

    Many grower make the mistake of pruning all lateral branches off as soon as possible. Their thought is that by removing low limbs the tree will grow taller, faster. However this is not the case.  Removing all laterals only serves to create a tall thin tree that bends over under it own weight, often snapping in a good wind storm. Nut production will also be delayed by over-pruning lateral limbs. 

    On my trees, I leave lateral branches on the tree until the tree has developed a nice full crown. At that point, I start to remove one or two low limbs each year. My goal is to develop a tree with 8 to 10 feet of clear trunk. However, it usually takes 12 to 15 years to get to that point.