November 9, 2018

Structural Pruning of Young Trees

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By: Jeremy Kranowitz

Our Crew Keep Indianapolis Beautiful (KIB) employees a crew of high school students and adult leaders who work to structurally prune trees planted by KIB three years ago (in 2012). This crew prunes young trees, in accordance with arboricultural best practices, to improve the physical structure of each tree. Our Goal Our goal in structural pruning is to improve the structure of each tree so that it can live as long as possible with as few structural defects as possible. If structural defects are not corrected while these trees are young, it could lead to these trees failing (breaking and falling) long before reaching maturity. Aesthetics Aesthetics are NOT a primary goal of structural pruning, which means that a tree that has been properly (structurally) pruned may not look as aesthetically pleasing as it did before the structural pruning. For most street trees, all branches that attach to the tree trunk between 0-10 feet above ground are temporary and will likely be removed, either through natural processes or human intervention. Though a young tree may look aesthetically different right after structural pruning, remember that at some point in the not-so-distant future, all of the current branches (attached within 10 feet above the ground) will be gone, and the new canopy will begin around 10 feet high and extend far upward from there. Pruning Debris Pruning generates debris (pruned branches). Our crew will create branch piles, in the right-of-way, near street intersections. The Indianapolis Department of Public Works has agreed to pick up these piles within a few days of the pile being created. Our Tactics We structurally prune using the following tactics:

Main stem: We identify the stem that we want to be the main trunk. After identifying the main stem, we either remove (or reduce the length of) all other stems that are competing to be the main stem.

The above images are from the Urban Tree Foundation: http://www.urbantree.org/structure1.shtml

Narrow angles of attachment: We identify any branches that are attached at a narrow angle to the trunk. These branches are at increased risk of failure. We either remove (or reduce the length of) these branches.

The above images are from the City of Rock Hill, SC website: http://www.cityofrockhill.com/departments/utilities/more/utilities/community-forestry/pruning-trees

Crown cleaning: We remove any tissue that is dead, dying, or diseased.

This image is from the Colorado State University Extension website: http://www.ext.colostate.edu/mg/gardennotes/615.html

Sprouts: We remove any suckers/ basal sprouts.

This image is from the Reeves-Reed Arboretum website: https://reeves-reedarboretum.org/cuttingarchiveDetail.php?Cuttings-29

Clearance: We remove branches to create clearance for: lines of sight to traffic signs, pedestrians, cyclists, and vehicles.

This image is from the My Yonkers website: http://myyonkers.net/tag/stop-signs/

Crossing/ rubbing: We remove branches that are crossing/ rubbing against other branches.

This image is from the University of Delaware Extension webpage: http://extension.udel.edu/ornamentals/files/2015/04/Prune-crossing-branches.jpg

Aesthetics: Aesthetics are not a primary goal of structural pruning, which means that a tree that has been properly (structurally) pruned may not look as aesthetically pleasing as it did before the structural pruning. The photo below is a before (left) and after (right) a tree that has been structurally pruned.

This image is from the Northern Pecans website: http://northernpecans.blogspot.com/2014_05_01_archive.html

Temporary branches: Though a recently (structurally) pruned tree may not look as aesthetically pleasing as it did before pruning, it may be helpful to remember that the aesthetic change is only temporary. A freshly pruned tree will fill out its canopy again. Also, all branches attached to the trunk from 0-10 feet are temporary and will eventually be removed. The below (left) image is of a newly planted tree in 2007. The image on the right shows the same tree in 2014 with nearly all original (temporary) branches having been removed as tree grew larger.