Wednesday, July 6, 2011

Training young pecan trees: The problem of stalked buds

    Early summer pruning and the forcing of rapid central leader growth can promote the development of stalked buds. Stalked buds are primary buds that form on short stems (photo at right). If stalked buds are allowed to grow into lateral shoots they will form a weak branch attachment characterized by a bark inclusion. The best way to explain how stalked buds grow into problem branches is with a series of photos.
    Here is a stalked bud that has started to grow and is now 8 inches in length (photo at right). Notice how a bark inclusion is already starting to form on the upper side of the shoot. Also in the photo is a leaf petiole (below the stalked bud shoot) and a secondary bud (between the stalked bud and petiole).
     Allowed to grow much larger, a stalked bud develops into a branch with a weak branch attachment and deep bark inclusion (photo at right).
    Weakly attached lateral limbs should be avoided when training young pecan trees. Limbs with deep bark inclusions tear easily from the tree, creating a huge scar on the trunk. In addition, when limbs with a deep bark inclusion are pruned off during normal "limbing up" operations, the pruning wound left behind does not callous over well. Without a well defined branch collar, the tree has a hard time growing over the bark inclusion.
     If you prune a pecan tree during the spring to force the growth of a central leader, by June you should see strong growth and the development of stalked buds (photo at left). This central leader has grown over 2 feet in height since I pruned to a single leader 5 weeks earlier and all this new growth is covered with stalked buds.
    Here is a close up of the same central leader. Notice that some of the stalked buds have even started to grow into lateral branches. The good news is that if you continue to practice the 2 foot rule you should end up pruning all of the stalked buds off the central leader. Often times the stalked buds are so green and tender that you can just pull them off by hand without using a pruning shear.
     As the tree continues to grow., you should note that the lateral branches that develop below your 2 foot central leader are actually developing from secondary buds left behind when the stalked buds are removed. Note in the photo at left you can see the pruning wound left behind after removing the stalked primary buds. Below that, secondary buds have broken and developed into well angled lateral shoots.

    The next post in the training young trees series is When to start training