Arborist News

This article is based on the upcoming revision of the ISA Tree Risk Assessment Best Management Practices and focused on some of the challenges and enhancements that will be implemented in the latest version. Learn the limitations of tree risk assessments and how uncertainty and subjectivity can affect tree risk ratings. Additionally, you will learn how tree risk rating is determined and the steps involved in developing a tree risk rating. 

The utility industry’s application of tree risk assessment practices differs from that of other commercial arborists working with clients who own individual or small groups of landscape trees. While utility tree risk assessors consider individual trees, risk is assessed and managed across very large populations of trees in proximity to overhead electric lines that compose the utility forest. Likelihood of impact and likelihood of tree failure are assessed independently and then combined to determine the likelihood of the tree or tree part failing and striking the utility target. The combination of likelihood of impact and failure is then used in considering the consequences of the strike failure, which defines the level of risk. 1 CEU (A, U, M, T, L, Bm)

Arborist News quizzes are available free online to members for one year after the date of publication; a maximum of six quizzes are available at any time. CEU quizzes for older articles may be purchased by both members and non-members.

This article reviews best practices for root pruning, including two different styles and how to execute them with minimal harm. Additionally, it will help arborists understand long-term effects of root pruning and how they can negatively affect tree health and stability. Arborists will also learn how to properly care for root-pruned trees to increase a tree’s chance for full recovery. 1 CEU (A, U, M, T, L, Bm, Bp)

Variegated plants possess leaves or petals that have patches or stripes of different colours. These trees and plants have gone in and out of fashion throughout history. When they are in fashion, the cost of purchasing variegated trees can be very high, and their production can be profitable for the nursery industry. Horticulturists have long been interested in the causes of variegation and the processes that may induce variegation because of the high financial value of variegated plants and because of variegations effect on plant health. 1 CEU (A, U, M, T, L, Bs)