Commercial Tree Risk Evaluation

Risk has two halves and both matter

Tree risk is not the same as tree condition. A tree can be in poor condition and represent almost no risk, or in reasonable condition and represent a great deal.

The first half is likelihood: how probable is failure, based on defects, species, and exposure. The second half is consequence: what is underneath, and what happens if it is struck.

A declining tree over a fenced detention basin scores badly on the first and negligibly on the second. The same tree over a fire lane is an urgent problem. That is why a useful evaluation ranks trees rather than simply listing their condition.

The defects that matter most

A handful of structural defects account for most commercial tree failures, and each one has a characteristic appearance.

Included bark at a branch union, where two stems grow tightly together with bark trapped between them, produces a joint that has no real wood connection. Those split, often in a wind event, and often taking half the tree.

Decay in the trunk or root flare, usually indicated by fungal fruiting bodies, cavities, or hollow sound. The tree can look healthy above while the structure supporting it is compromised.

Root damage from trenching or paving, which removes anchorage on one side. This is the most common defect nobody notices, because the work that caused it happened years earlier.

And previous poor pruning, particularly topping, which produces fast weakly attached regrowth exactly where the tree was cut.

What to do with the findings

The output of an evaluation is a ranked list, and the value is in acting on the top of it rather than reading the whole thing.

Highest priority work should be scheduled immediately, not put into a budget cycle. That is the point of ranking.

Middle priority work goes into the next budget with a date attached. Low priority items get a monitoring interval and a note, so they are looked at again rather than forgotten.

The one thing that should not happen is a full report that gets filed. A documented evaluation identifying a hazard, followed by no action, is a worse position than never having assessed at all.