ISA offers a variety of educational materials to help arborists improve their arboricultural knowledge. Each week we will feature a product, or group of products that will enhance your arboriculture education. This week, ISA is featuring The CODIT Principle by Dirk Dujesiefken and Walter Liese.

“This book has a long history,” said Dujesiefken. “In the year 1984, Alex Shigo came to Europe and he said what we were doing with our trees was wrong. That was the reason why we started researching pruning and the tree’s reaction at the University of Hamburg.”

This must-have resource for arborists offers an in-depth look at a tree’s physiologic response to wounding and helps arborists understand wound reactions of bark cambium, and wood, as well as the factors that influence the tree’s response.

The CODIT Principle is the result of 20 years of research, not only from Dujesiefken, but his colleagues from Australia, Slovenia and the United States.

“There are two types of readers, the researcher and the practitioner,” Dujesiefken said. “We’ve received a lot of comments from practitioners stating that it helps to understand how trees grow and how they defend themselves.”

This resource helps readers understand the complex responses more easily, the authors further developed Shigo's 1977 CODIT Model into the broader CODIT Principle, which describes the reactions from injury to rot encapsulation as a series of phases. The CODIT Principle clarifies why some wounds have problematic consequences for the tree while others do not.

“We wanted to explain how trees grow and react after several damages, understand what the tree will and able to do and not do,” Dujesiefken said. “Furthermore, we want to explain the biology of the tree, so that people will understand why arborists do things in a certain way.”