Old City heritage tree inspected by expert for public safety


A tree listed on the City of Nanaimo's registry of Heritage trees was recently inspected by a Vancouver Island tree expert to determine if it should be cut down for public safety reasons. Dr. Julian Dunster was hired to perform an advanced risk assessment of the tree, a Catalpa bignonioides, located in front of 321 Wesley Street.

By using sonic tomography and resistograph drilling, Dr. Dunster was able to confirm there is extensive decay and structural issues throughout the trunk and major limbs. However, the decay is isolated and slow spreading and given other factors, such as the light weight wood of Catalpa trees and relatively sheltered location, the tree can safely stay where it is for the time being. The City will receive a full report of Dr. Dunster's findings later this week.

Strategic Link: Public Safety; Environmentally Responsible; Cultural Vitality

Key Points

  • Due to the historical significance of the tree, the decision to retain or remove it needed to be based on a thorough understanding of its structural integrity, biomechanics and the extent of decay.
  • Despite the large amounts of decay, the tree is still in good condition and, with proper maintenance like pruning, it can safely stay where it is.


"Like all living things every tree will eventually decline and die. In an urban environment it can be difficult to balance the desire to preserve our living heritage with the need for public safety. Fortunately in this case with the use of the latest technology and a thorough understanding of tree biomechanics we were able to determine that with some mitigation keeping this beautiful tree in the Old City Quarter posses an acceptable level of risk. "

Urban Forestry Coordinator
City of Nanaimo

Quick Facts

  • Sonic Tomography uses sound waves bouncing from points around the circumference of the trunk or limb to generate an image of a cross section of the tree.
  • A Resistograph is an instrument that drills a small hole in the tree while measuring the resistance of the wood against it, it generates an accurate picture of the composition of that part of the tree.


Dr. Julian Dunster setting up tomography equipment
Dr. Julian Dunster setting up tomography equipment
Dr. Julian Dunster scanning the tree
Dr. Julian Dunster scanning the tree


Patrick McIntosh
Urban Forestry Coordinator
City of Nanaimo
250-755-4460 Ext: 4357

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