Have you ever wondered how that tree you bought at the nursery got such a straight trunk?An ideal young shade tree specimen should have a single straight trunk from the roots to the very uppermost bud. Nursery growers maintain the single leader until the tree is too tall to prune then it is allowed to form the rounded multi-stemmed canopy we are familiar with in mature shade trees. IN the nursery business we call this pruning concept 'Leader Training'. The goal is to end up with a nice straight single trunk in a shade tree.

Trees grow at the branch tips where the apical bud, the leader as it were, suppresses other buds behind it. The apical bud produces auxin, a plant growth regulator. This chemical allows the bud to maintain its position as leader by reducing the growth of its competitors.

Remove the apical bud and the chemical is gone and all of the other buds are released beginning a mad dash try to assume the leader’s former role. This results in bushy growth with one or more branches that are equals. These equal branches compete for resources and space. Eventually, they can create weak spots in the trunk leading to the tree splitting.

The point is to aid a single leader to maintain its position in the canopy of the tree. Tree owners can do this by pruning out any competing leaders up to a certain height. This type of pruning may be done throughout the summer. Use a pole saw (watch out for power lines!) and prune the other branches at least six inches behind the desired leader. A stub of one of the removed branches can be left and the single leader may straightened and taped to this stub with masking tape. The masking tape will last long enough to correct the leader’s growth but will rot soon enough to prevent future damage.

Some trees need more attention than others. Maples are notorious for wanting to form big round canopies at three feet from the ground. Oaks tend to want to form single leaders. Keep a close eye on your young shade trees to maintain single leaders. If you are unsure of how to do this type of pruning consider hiring a professional arborist.

You can learn more about pruning by downloading our Pruning Trees and Shrubs Publication.