What a Tree Risk Assessment Actually Involves
Risk is not the same as defect. A hollow tree in the middle of a hay field is a defect with almost no risk. The same tree over a child's bedroom is an emergency. A proper assessment weighs both halves of that sentence.
This is the framework a professional uses, so you can tell whether the opinion you are getting is an assessment or a sales pitch.
Key Takeaways
- Risk combines likelihood of failure, likelihood of impact and severity of consequence, not defect alone.
- Ground inspection covers root flare, trunk, unions and canopy, with sounding to find hollows.
- Saturated clay soil makes root failure the leading cause of whole tree failure in Lafayette County.
- Ask for an assessment before buying a property, after any storm and before construction near the root zone.
- Reducing end weight, cabling or moving the target are often valid alternatives to removal.
Three Things Get Scored
The first is likelihood of failure: how probable is it that this part of the tree comes apart within a defined time frame, based on decay extent, crack depth, union quality, lean change and root condition.
The second is likelihood of impact: if it fails, does it hit anything? A limb over an unused side yard scores far lower than the same limb over a driveway where cars park all day.
The third is consequence of impact: a small dead branch onto grass is negligible; a 30 inch leader onto a roofline is severe. Combining the three gives a rating that tells you whether to act now, monitor annually or leave it alone.
What Gets Inspected On Site
From the ground: root flare and soil for cracking or lifting, trunk for cavities, seams, conks and old wounds, unions for included bark, canopy for deadwood, dieback percentage and end weight distribution. A mallet sounding of the lower trunk reveals hollow sections that look solid from outside.
In north Mississippi we pay extra attention to root condition, because saturated clay after a heavy rain is where most whole tree failures start, and to species specific patterns such as hypoxylon canker on stressed oaks and pine beetle activity on loblolly.
When To Ask For One
Before buying a property with mature trees close to the house. After any storm that took limbs out of a canopy, because remaining hangers and cracked unions are not visible from the porch. Before construction, since grading and trenching within the root zone kills trees on a two to five year delay. And annually for any tree already flagged as a monitor.
Insurance and HOA disputes are another common reason. A written assessment documenting a hazard before it fails is worth considerably more than an opinion after.
Mitigation Is Not Always Removal
Options between doing nothing and cutting it down include crown cleaning to remove deadwood, end weight reduction on overextended limbs, cabling or bracing a weak union, moving the target such as relocating where cars park, and restricting access under the canopy. A good assessment presents the range and the cost of each, not a single number to sign.