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Dr. Alex Shigo

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Shigo's Pruning Method

Shigo's Pruning Method

TAMU.edu
Dr. Alex Shigo was widely considered the "father of modern arboriculture" and a university trained tree pathologist. Dr. Shigo's study of tree biology led to a broadened understanding of compartmentalization of decay in trees. Shigo's ideas eventually led to many changes and additions to commercial tree care practices and the now accepted way to prune a tree.

Full Name:

Dr. Alex Shigo

Date of Birth:

May 8, 1930

Place of Birth:

Duquesne, Pennsylvania

Education:

Shigo received a bachelor's of science degree from Waynesburg College near Duquesne, Pennsylvania. After serving in the U.S. Air Force, Shigo continued his study of 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 / Ph.D. in pathology in 1959.

U.S. Forest Service Career:

Dr. Shigo started a career with the United States Forest Service in 1958. His earliest assignment 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 have the ability to contain disease by creating compartments.
Shigo became Chief Scientist for the Forest Service and retired in 1985.

Date of Death:

Dr. Alex Shigo, 86, died on October 6, 2006

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 {Barrington, New Hampshire}, going to his office after dinner when he fell going down the steps, landing on the patio, and died from a broken neck."

CODIT:

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. Shigo disputed the validity of many techniques that the arboricultural industry has used for over a century. His work "proved" that old techniques were shown to be unnecessary or, even worst, harmful. In Alex Shigo's defense, his conclusions have been confirmed by other researchers and are now a part of current ANSI standards for tree pruning.
Bad news is, many commercial arborists continue to perform flush cuts, toppings, and other practices that Dr. Shigo's research shows 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.

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