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The Basics of Tree Pruning

MERISTEM TIPS :: VASCULAR SYSTEM :: TRANSPIRATION :: THE 1/3 RULE
THE BRANCH COLLAR :: TARGET PRUNING :: CONCLUSION :: GLOSSARY


THE 1/3 RULE
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Canopy reduction is often needed to preserve a tree, when site conditions limit its size.
The 1/3 rule is a way to determine if there will be enough meristem tips left to maintain sap pressure after a pruning cut is made.

 

We see in this representation of a tree, we have a leader compounding into two laterals. A legitimate cut of reduction would be to eliminate one of the two laterals. One must leave a branch at least one third the diameter of the former leader in order to maintain the sap flow and the energy flow all the way to the branch tips.

 

 

 

Leader B is at least one third the diameter of stem A, so this could be considered a legitimate cut, and the tree will continue, and sustain, and heal the cut.


 

The 1/3 Rule is a general guideline, and does not apply in all situations. Sensitive species such as birch and citrus may require more delicate treatment. Of course, the more you know about your tree, the more successful your management efforts will be.

 

Now let’s return to our example tree, where we would like to remove a large lateral in contact with the nearby roof, with-out endangering the tree’s health.

 

 


 

We see that the leader is at least one third the diameter of the lateral, and we can remove the branch that is interfering with the roof, with the expectation that the tree will heal the wound.

 

 

 

When we first observed the tree, we saw a branch that was a potential hazard to the house.

 

 

 

We removed the limb at the branch collar, following the one third guideline.


 

In that way, we maintained the form and health of the tree, and sent it into the future.

 

 
     

I.S.A. Certified Arborist WE-4370A

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