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Dr. Alex Shigo: A Short Biography

Dr. Alex Shigo was a renown biologist and plant pathologist. He is widely considered the father of modern arboriculture. Shigo’s study of trees and their internal processes revolutionized the tree care industry, leading to a broader understanding of tree decay, compartmentalization, and wound recovery.

Early Life and Education

Alex Shigo was born in Duquesne, Pennsylvania in 1930. He received a bachelor’s degree of science from Waynesburg College in southwestern Pennsylvania. After serving in the U.S. Air Force during the Korean War, Shigo returned home to further his studies in botany, biology, and genetics, working as a lab assistant under his former biology professor, Dr. Charles Bryner.

Shigo enrolled at the University of West Virginia, receiving a master’s degree in biology in 1958, and a Ph.D in pathology in 1960. He joined the U.S. Forest Service later that year, specializing in the study of tree biology. He remained with the U.S. Forest Service until he retired as chief scientist in 1985. Upon retirement, Alex Shigo founded Shigo and Trees, Associates, which publishes technical booklets and CD’s based on Shigo’s body of work.

Innovations and Discoveries

Alex Shigo’s primary mission was to care for trees. He often suggested that people “touch trees” in order to gain insight into how they functioned. Shigo sought trees in their natural settings, using what he observed to inform his work and theories.

With the assistance of the newly invented one man chainsaw, Shigo dissected trees longitudinally as well as horizontally, an innovative approach that scientists had not yet attempted. This enabled him to study the internal structure of trees from unique perspectives.

Through his observations, Shigo determined how trees respond to injuries and infections. He discovered that they did not restore or repair damaged cells. Instead, the surrounding cells would transform themselves chemically and physically to prevent the spread of decay. The tree would then seal the wounded area with a ring of callus, a process Shigo referred to as compartmentalization.

Inspired by these revelations, Shigo pioneered new concepts of pruning. He developed the three cut pruning method, which, when applied, avoided damaging the branch collar and branch bark ridge of limbs. This allowed pruning wounds to close more naturally, preventing infestation from insects, and decay.

Through further study, he deduced that flush cutting, the standard pruning practice of the time, harmed trees, reducing their ability to effectively seal wounds. He argued against tree topping, describing how it destroyed a tree’s natural structure, stripping it of vital growth. He also challenged the notion of wound dressing, in which arborists would attempt to seal a pruning cut with a dressing composed from paint compounds, tar, or other similar materials. He explained how dressing a wound often created a moist environment for insects and pathogens to thrive in.

At first, many objected to his ideas, disputing their accuracy. But as the evidence mounted, Shigo’s theories were vindicated, leading to many changes in the tree care industry.

After having spent his life interacting with trees, and encouraging others to do the same, Alex Shigo died in his New Hampshire cottage on October 6th, 2006.

Image courtesy of The Shigo Family

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