By Larry Hodgson
Many conifers have a naturally pyramidal shape. This is the case of, among others, firs (Abies), spruces (Picea), pines (Pinus) and larches (Larix). They’re called whorl-branched conifers, because a whorl of new branches appears near the stem tip each spring. They all have a main trunk topped off by a single terminal shoot called the leader. As long as the leader is healthy, symmetry is maintained. This is called apical dominance.
But if the tree loses its leader, and that can be caused by insects, disease or physical damage, its future symmetry is threatened. Fortunately, that’s something you can fix. And there are two ways of going about it.
The first technique simply starts out by allowing the tree to grow on its own. Since whorl-branched conifers only put on new growth in spring, you may have to wait until the following spring to see what happens. Typically, the conifer will then produce not only one terminal shoot near where the old one was lost, but two or more. Or sometimes side branches near the top start to grow vertically and thus start to become leaders. Typically, there are also usually two or more.
Since, for symmetry’s sake, you can’t allow your conifer to produce multiple leaders, you’ll have to make a choice. Pick whichever new leader appears the strongest and remove all the others. By doing so, you’ll restore apical dominance and the conifer will resume its expected symmetrical growth.
The other method is to be proactive. As soon as you realize the leader is dead, broken or missing, choose a side branch and direct it upward. You can do this by fastening the branch to the stub (if there is one) with twist ties. If there is no stub, simply attach a stake to the trunk and fix the side branch to it so it remains upright. It will quickly come to dominate the other branches and react like a leader (terminal shoot).
When this new leader has lignified enough to hold its shape, usually 3–8 months later, just remove the ties and the stake. Apical dominance will have been restored and the tree will then resume its attractive pyramidal growth pattern.
Article originally published on July 12, 2015.