Friday, June 26, 2015

Shaping a young tree with summer pruning

      This month I revisited a young tree I had pruned during the dormant season (photo at right). I was very interested to see how the tree reacted to my earlier pruning cuts and just where and how the new branch growth would develop in the spring.
   Here's a photo (at left) of the same tree--after pruning in March and once the tree has grown new shoots and leaves in June.  When I first pruned this tree, the only lateral branches that had good wide-angled branches attachments were in an area right above the graft union (near the blue tape). Above that, I had 3 1/2 feet of clear central leader. This is definitely not an ideal situation. This tree needs lateral branches to help balance the tree and promote trunk diameter growth.
   As you can see, the short lateral branches I left on the lower portion of the tree burst forth grew over two feet in length. At the top of the tree, I still have a central leader but several strong lateral branches have developed just below. These are growing rapidly and are starting to compete with the leader for sunlight. In the middle portion of the main trunk, I have some lateral branches forming but they growing with less vigor. To shape this tree further, I made several summer pruning cuts to help direct the trees growth into the summer.

    I started by working on the bottom of the tree (photo at right). The yellow arrow points to a rapidly growing shoot that originated with one of the short laterals left during the dormant pruning process. To prevent this shoot from overtaking and shading out weaker shoots above, I cut the shoot back to an outward-facing bud. 
   The red arrow points to a shoot that originated from a bud on the main trunk. This shoot has grown nearly two feet in length, so I decided to pinch out the terminal and force the branch to pause it's extension growth, mature remaining leaves, and build shoot diameter.
   These were not the only lateral branches I pruned. I made similar cuts to lateral shoots around the entire tree.

   At the top of the tree, I followed the 2-foot rule and pruned the terminals of lateral branches below the central leader. I also spent some time to remove all the stalked buds I found growing in each leaf axil on the central leader. Red arrows in the photo at left point to several of these stalked buds and the comparison photo shows the central leader after all the buds have been removed.

   The photo at right shows the entire tree after summer pruning. This tree illustrates key principles of directive summer pruning: Encourage the growth of a central leader, promote lateral limb formation, but keep lateral extension growth in check.