Biography of Dr. Alex Shigo

Dr. Alex Shigo pointing out markings on an Oak section on a red pickup truck

Max Wahrhaftig / Wikimedia / CC BY 3.0

Dr. Alex Shigo (May 8, 1930-October 6, 2006) was a university-trained tree pathologist who was widely considered the "father of modern arboriculture." Dr. Shigo's study of tree biology led to a broadened understanding of the compartmentalization of decay in trees. His ideas eventually led to many changes and additions to commercial tree care practices, such as the currently accepted tree pruning method.

Fast Facts: Alex Shigo

  • Known For: Pioneering tree-friendly pruning
  • Born: May 8, 1930 in Duquesne, Pennsylvania
  • Died: October 6, 2006 in Barrington, New Hampshire
  • Education: Waynesburg University, West Virginia University
  • Published Works: "Tree Pithy Points," "Compartmentalization of Decay in Trees," "A Tree Hurts, Too," "A New Tree Biology and Dictionary," "Tree Anatomy," "Tree Pruning Basics," "Modern Arboriculture: A Systems Approach to the Care of Trees and Their Associates," and more
  • Awards and Honors: Chief Scientist for the U.S. Forest Service
  • Spouse: Marilyn Shigo
  • Children: Judy Shigo Smith
  • Notable Quote: "Many people spend time on what goes wrong with a tree; I wanted to study what goes right."


Shigo received a bachelor's of science degree from Waynesburg College near Duquesne, Pennsylvania. After serving in the Air Force, He continued to study botany, biology, and genetics under his former biology professor, Dr. Charles Bryner.

Shigo moved from Duquesne and continued his education at the University of West Virginia, where he received a combination Masters and Ph.D. in pathology in 1959.

Forest Service Career

Dr. Shigo started a career with the U.S. Forest Service in 1958. In time, he became Chief Scientist for the Forest Service and retired in 1985. His earliest assignment, however, was to learn more about tree decay.

Shigo used a newly invented one-man chainsaw to "open" trees in a way no one else had, by making longitudinal cuts along the stem rather than transverse cuts across the stem. His tree "autopsy" technique led to many important discoveries, some of which were and are controversial. Shigo believed that trees are not made up of "mostly dead wood" but rather can contain disease by creating compartments.


Shigo found that trees respond to injuries by sealing the wounded area through the process of "compartmentalization." This theory of "compartmentalization of decay in trees", or CODIT, was Shigo's biological brainstorm, leading to many changes and adaptations in the tree care industry.

Instead of "healing" like our skin, an injury to a tree trunk results in surrounding cells changing themselves chemically and physically to prevent the spread of decay. New cells are produced by cells lining the cut area to cover and seal the injured area. Instead of trees healing, trees actually seal.

The Controversy

Dr. Shigo's biological findings are not always popular with arborists. His findings disputed the validity of many old techniques that the arboricultural industry has used for over a century and taken for granted as undeniably true. His work showed that the traditional methods were unnecessary or, even worse, harmful. In Shigo's defense, his conclusions have been confirmed by other researchers and are now a part of current ANSI standards for tree pruning.

The bad news is that many commercial arborists continue to perform flush cuts, toppings, and other practices that Dr. Shigo's research showed to be harmful. In many cases, arborists perform these practices knowing they are harmful, but believing their business cannot survive by practicing their craft under Shigo guidelines.

Circumstance Surrounding Death

According to the Shigo and Trees, Associates website, "Alex Shigo died on Friday, October 6. He was at his summer cottage at the lake, going to his office after dinner when he fell going down the steps, landing on the patio, and died from a broken neck."

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Nix, Steve. "Biography of Dr. Alex Shigo." ThoughtCo, Sep. 22, 2021, Nix, Steve. (2021, September 22). Biography of Dr. Alex Shigo. Retrieved from Nix, Steve. "Biography of Dr. Alex Shigo." ThoughtCo. (accessed March 27, 2023).