For the life of your trees. · (856) 241-0489
TCIA AccreditedNJ LTE #408TRAQISA Member
ISA’s Tree Risk Assessment Qualification gives you the framework. The resistograph gives you the wood. Used together, they turn an ambiguous decay wound on a beloved White Oak into a measurable, baseline-able, decision-grade assessment.
The hardest tree-care conversation a homeowner has is the one about a tree they love. Old. Beautiful. Significant to the property. And now showing a decay wound at the base, in a spot they can’t stop looking at every time they walk past it. The honest answer to “what does it mean” needs both science and judgment, and it depends on a structured method for getting at the inside of a tree without taking the tree apart. That’s the work in this clip.
View from the Field · Paul Biester · Tree Awareness
TRAQ — ISA’s Tree Risk Assessment Qualification — is the standardized framework that international arboriculture has converged on for evaluating tree risk. It works on three axes simultaneously: the likelihood of failure (what’s the structural condition of the tree?), the likelihood of impact (if the tree fails, does it hit something that matters?), and the consequences of impact (how bad is the outcome?).
One of the methodology’s most useful pressures is that it makes the arborist commit to a written assessment, with reasoning attached. You can’t hand-wave a TRAQ report. Either the tree poses a risk that justifies intervention or it doesn’t, and the underlying logic is documented.
TRAQ tells you what to assess. The resistograph tells you what’s actually inside the wood. It’s a small, hand-held drill that measures the resistance of the wood as a fine bit penetrates the trunk — and outputs a graph of that resistance over the depth of the bore. Solid wood reads as high resistance. Decayed wood reads as low. Hollow voids read as essentially zero. The technician sees, on a printed strip or a screen, exactly where the strong wood is and where it isn’t.
This is non-destructive in any practical sense. The bore is small enough that the tree closes it the same way it closes any minor wound. What you get back is a cross-section of the trunk that no visual-only inspection can see — and on a tree where the question is “how much structural wood is left,” that data is decisive.
“We got a call from a client about this really cool White Oak tree they have in their backyard. They noticed an area of decay that had opened up on the bottom. So I’m here to take a closer look at this wound. I’m going to first assess the amount of internal decay in the tree, then get a baseline for the size of the wounding, and then do some follow-up care and just get a sense of: is this wound expanding, or is this tree able to compartmentalize this wound?”Paul Biester · NJ LTE #408 · TRAQ
Step 1 — Visual reading. Color tells the story first. Dark staining inside bark fissures is a signal that something’s going on underneath. The flat spot in a buttress root that should be a normal flare is a signal of constriction below grade.
Step 2 — Sounding. A simple hammer or mallet against the trunk produces a different tone over solid wood vs. detached or decayed wood. It’s a fast, cheap, surprisingly accurate first-pass screen.
Step 3 — Bark exploration. Where the sounding suggests detached bark, Paul peels carefully to see what’s underneath. On this tree the discovery is interesting: the wound has formed wound closure tissue (live cambium) underneath what looked like detached bark. This tree has been fighting this wound.
Step 4 — Below-grade investigation. The flat-side root flare gets a shallow, careful exploration with a hand tool. Fibrous root concentration close to the surface is suggestive — possibly a girdling root constricting vascular tissue and allowing decay to colonize.
Step 5 — Resistograph drilling. The targeted finish. Paul drills directly through the face of the suspected wound to read the wood’s actual condition behind it. The reading is informative: some soft wood at the surface, more resistance behind it than expected. Better than predicted.
Step 6 — Baseline and re-assess. Wound dimensions measured. Photographs taken. The plan is to come back in 8–12 months and run the same assessment to see if the wound is expanding or holding. The decision between “remove” and “keep” is deferred until the data supports it.
This is the difference between tree care that operates on visible symptoms and tree care that operates on actual data. A decay wound at the base of a beloved oak is the kind of thing that produces immediate “take it down” recommendations from contractors who don’t have the tools or the patience for proper assessment. On this tree, the proper assessment found a tree that’s actively fighting the wound, with healthy wound closure happening, and resistograph data that suggests more usable structural wood than the surface decay implies.
Paul ends the clip with the line that earns its place: this work definitely requires a good bit of science, a good eye, and quite frankly a good bit of intuition — just experientially looking at these things over time and having that database in your head. TRAQ supplies the framework. The resistograph supplies the data. Neither one supplies the experiential pattern recognition that comes from 30+ years of looking at trees with similar wounds and watching what happened next.
For a TRAQ-qualified visual + resistograph assessment on a high-value tree, request a Tree Risk Assessment →
