Silver Maples form weak unions that look fine from the outside. The resistograph reads what’s inside the wood.
Silver Maple is one of the most common large hardwoods in suburban South Jersey landscapes — fast-growing, often beautiful at maturity, but with a reputation for weak wood and structurally suspect limb attachments. When a homeowner has a heritage Silver Maple with a questionable union, the question isn’t whether the wood looks weak from the outside. The question is what the resistograph reads when it bores through it.
View from the Field · Paul Biester · Tree Awareness
“Through resistograph technology, an arborist is able to detect wood decay, stages of rot, hollow areas, cracks and ring structure. The resistograph is an ideal device for estimating tree stability and longevity.”Paul Biester · NJ LTE #408
Silver Maples (Acer saccharinum) commonly form co-dominant stems with included bark — two leaders growing from a tight V-shaped union, where bark gets trapped in the crotch instead of the wood fully bonding. From the outside the tree looks like a single robust trunk. Inside the union, the connection between the two stems is structurally compromised in ways that no visual-only inspection can confirm or rule out.
This is exactly the situation the resistograph was designed for. A small drill bit advances into the suspected weak union. As it travels, it logs resistance — high through solid bonded wood, low through the included-bark seam, near-zero through any actual cavity. What you get back is a printed cross-section of the union’s internal structure, on a scale of accuracy no other field tool produces.
The data picture changes the conversation in several specific ways.
Decay vs. healthy wood. Solid xylem reads at a consistent baseline resistance. Decayed wood reads progressively lower as fungal degradation breaks down cell walls. The resistograph quantifies how much of the cross-section is still functional structural wood vs. how much has been lost to decay.
Stages of rot. Early-stage decay (incipient) reads slightly lower than healthy wood. Advanced decay reads dramatically lower. The trace tells you where in the disease progression you actually are.
Hollow areas. True voids — cavities where the wood has been fully consumed — read as essentially zero resistance. The width of the zero zone on the trace tells you the cavity diameter.
Cracks and seams. Discontinuous drops in resistance across the bore signal cracks or detached layers. Critical for evaluating included bark unions.
Ring structure. The repeating pattern of growth rings shows up as a fine resistance fluctuation across the bore. Strong, even ring structure is a positive signal of healthy long-term growth.
For the Silver Maple in this clip: the resistograph reading provides the structural baseline. If the union shows enough solid wood to justify keeping the tree on a monitoring + cabling protocol, that becomes the recommendation. If the reading shows the structural cross-section is below the threshold a Silver Maple of that size needs to safely hold a heavy canopy, the recommendation shifts to removal.
Either decision is defensible when the data supports it. Neither is defensible without the data.
Most of the large Silver Maples in residential South Jersey neighborhoods were planted in the 1950s–1970s as fast-growing shade trees. They’re now 60–80+ years old — closer to their natural lifespan limit than most homeowners realize, with predictable structural defects from a species known for them. The right relationship with these trees is structured monitoring, not panic-removal-on-failure.
If you have a mature Silver Maple with a target zone over a structure, a TRAQ + resistograph assessment determines whether the tree justifies cabling and monitoring or whether removal is the responsible call. Request a Tree Risk Assessment →
