Ask an Arborist: The ABC's of Pruning 

This is part three of a three-part dormant pruning series. Watch Ask an Arborist: The Rules of Pruning to catch up on part two.
When pruning your trees, there are steps you can follow to ensure you are making the proper cuts and not removing too much off your tree. Tree experts Andrew Pleninger and Chris Luley created The ABCs Field Guide to Young and Small Tree Pruning to help guide the pruning process. The rules of the ABC’s will tell you where to start, what branches to prune, and when you are finished. Follow these rules to help get you started on your tree pruning.
Step A: Assess the tree
o How is the tree growing? Is it healthy?
o What is the setting? Does human activity dictate a desired form for the tree?
o What species is it? What is its natural form? Is it a ‘shade’ tree or ‘ornamental’ tree? This will dictate how you prune.
Step B: remove Bad branches
o Start with the three ‘Ds’ - dead, damaged, and diseased.
o Next, look for branches that are rubbing, or those weakly attached.
o Look at the tree, and the pile of branches removed so far, if you haven’t reached any of the limits in the ‘five factors,’ continue.
Step C: remove or reduce Competing branches
o You identified the central leader in Step One; now we want to address any competing branches:
 Co-dominant stems: it’s best to keep this cut as small as possible, so complete removal is usually best.
 Competing laterals: these are branches that have a shoot headed upward at the same height as the leader.
o Next, focus on areas where multiple branches connect to the trunk at the same place. Develop better branch spacing by removing one each year, starting with the largest one first.
o Next, consider clearance: these temporary branches in the lower third of tree height improve trunk strength, but may need to be shortened.
o Finally, consider crossing (not rubbing) branches or chances to improve vertical branch spacing.
Every pruning cut is a new chance to observe the tree in light of the “five factors;” stop pruning when any of the factors are reached.
If we focus our pruning efforts strategically - with the right tools - we can develop long-lived urban trees.
Have a tree question you want answered? Tweet @arborday with #AskAnArborist .
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