Health check for city's trees

Some of the city’s oldest trees are being subjected to a thorough analysis as part of Wagga Wagga City Council’s tree audit.

Council are working with a team of independent tree auditors to assess trees in a staged city audit. The areas being covered in 2020 include Ashmont, Central, North Wagga Wagga, Turvey Park and the Wagga Wagga Botanic Gardens.

Team Leader Tree Maintenance Andrew Oliver explained that safety is the team’s main aim when assessing the trees.

“We want to ensure our trees are safe, for both people and property,” Mr Oliver said.

“We’re using a dedicated tree risk assessment software program, which quantifies all the issues we find in a tree and gives each tree a risk score. We’re then able to program our works based on those scores. Trees that are deemed high-risk are our priority.”

The team systematically work from the ground up, looking at a tree’s overall health and structure.

“I start off by looking at the roots; any heaving or cracking in the soil can indicate movement, which may be a sign of total tree failure,” Mr Oliver said.

“Once that’s ruled out, you look up the stem (trunk). Often people think a high stem is dangerous, but it’s not the height that’s an issue, it’s the amount of residual timber (living tissue) around the diameter of the stem that’s important. We work on a ratio of 1-to-6, so for example, if we’ve got a stem diameter of 36 inches, we require a minimum 6 inches of residual timber for that tree to be safe.”

The team then check for dead wood, and assess limbs and the way they’re attached, looking for telltale bulges in bark that may indicate an underlying problem.

“There are only two things a tree can do with a defect,” Mr Oliver said.

“It can compartmentalise it and seal it off, or it can put on mass and try to outgrow it – effectively stabilising itself by distributing the load.”

Council is working with Homewood Consulting, a leading arboricultural firm, to conduct the audit over the next few weeks.

If you’d like to contact Council about a public tree, visit wagga.nsw.gov.au/servicerequests or call 1300 292 442.

Image: Team Leader Tree Maintenance Andrew Oliver is part of the Council team ensuring the city's trees are healthy and structurally sound.