Pruning: Removal of Codominant Leader
This works for shrubs as well as most big species like cedar, maple, birch, etc.
Copyright M. D. Vaden: 2010
Here is a short brief video showing the removal of a small codominant leader from a young hornbeam. This pruning principle works for big trees or small ones. Even some shrubs.
When leaders develop forming a "V" shape, the stems can split apart rather easily many times from wind, snow, ice or even rain weight on leaves. Because as the stems grow and expand, the two eventually touch one another, preventing future expansion of tissue in between. And the bark just touches in the middle, but generally does not bond together. It's unlike a "U" shape union where wood tissue can keep building-up each year.
These can be removed when larger, like with 2 inch or 6 inch diameter cuts, but it's typically much better to do early when the cuts are smaller. The other reason is that less of hole is opened in the canopy. Suppose a 5 inch diameter cut is made; then the leader may be 12 feet long and open up a 12 gap in the upper canopy. So much better to make a 1/2 inch cut and open a sliver in the canopy of leaves.