1 and 2: Dead wood and a dying crown
More than a quarter of the crown dead, or large dead limbs, is a sign the tree is failing. Dead wood becomes brittle and drops without warning.
3 and 4: Cracks and cavities
Long vertical cracks in the trunk, splits at branch unions and large cavities weaken the structure. A small cavity may be fine; a large one that goes deep is not.
5 and 6: Fungus and decay
Mushrooms or shelf fungi on the trunk or base mean wood is decaying inside. They are often the last sign before failure.
7 and 8: Lean and heaved soil
A new lean, or a lean that is getting worse, along with soil lifting or cracks at the base, shows roots letting go. A tree that has always leaned and looks stable may be fine.
9 and 10: Poor structure and damage
Codominant trunks with a tight V-shaped union, roots cut by construction and trees hit by lightning or storms can be dangerous. A tree can show several of these signs at once.
What to do next
Keep people and cars away from the fall zone, take photos and call an arborist. Many trees with one issue can be saved with pruning or support.
Any tree with a defect near a house or a walkway deserves a professional look soon.
