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Published 2026-09-29

Is My Tree Dangerous? Warning Signs to Check

A tree is dangerous when something about it is likely to fail and there is something underneath it could hit. The warning signs are dead or hanging branches, cracks and splits (especially where two trunks meet), fungus on the trunk or at the base, a lean that is new, and soil lifting or cracking around the roots. If a tree is near a power line, stay away and call Hydro Ottawa; if it is a City tree, call 3-1-1; if it is yours and threatening your house right now, it can be removed without waiting for a permit.

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The warning signs

Walk around the tree and look up, then down:

  • Dead branches, especially large ones over a roof, driveway or play area, and any branch broken and hanging in the crown.
  • Cracks or splits in the trunk or a main limb, and tight V-shaped forks where two trunks are pushing apart.
  • Mushrooms or shelf-like fungus on the trunk or around the base, a sign of decay inside.
  • A lean that was not there before, or soil lifting and cracking on the side away from the lean.
  • Cavities, missing bark, or a crown that is thinning or dying back year after year.
  • Recent digging, paving or construction near the roots.

What it could hit matters as much as its condition

A dead tree at the back of a large lot with nothing under it can wait for a planned job. A tree with the same problems over a house, a car, a fence, a neighbour's yard or a sidewalk cannot. When you judge urgency, picture where it would land.

Power lines and City trees

Never touch, climb or prune a tree that is touching or close to a power line, and after a storm treat every downed line as live. Keep everyone back and call Hydro Ottawa. Trees on the City's boulevard or in a park belong to the City of Ottawa: report a dangerous one to 3-1-1.

Your own tree: permits and emergencies

Under Ottawa's Tree Protection By-law, a private tree that is an immediate threat to public health and safety can be removed without a permit. The City asks you to photograph it first as evidence of its condition. A tree that is dangerous but not an immediate threat usually needs the normal permit process if it is 30 cm or more across on an urban lot of one hectare or less.

Bisson Services offers 24-hour emergency service for dead, dying and dangerous trees across Ottawa and Prescott-Russell. If it is already cracked, hanging or leaning onto something, call (613) 558-4806 now. Otherwise, see tree removal or ask for a free estimate; sometimes the answer is pruning out one bad limb rather than taking the tree down.

Common questions

How do I know if a tree is about to fall?

Watch for a new lean with soil lifting or cracking on the far side, large cracks or splits in the trunk, fungus at the base, and roots damaged by digging. Any of these near a house or driveway needs a professional look soon.

Who do I call about a tree near a power line in Ottawa?

Hydro Ottawa. Never touch or prune a tree near a power line yourself, and treat any downed line as live.

Do I need a permit to remove a dangerous tree in Ottawa?

Not if it is an immediate threat to public health and safety; photograph it first. Otherwise, a private tree 30 cm or more across on an urban lot of one hectare or less needs a City permit.

More guides

What to Do With Wood Chips After Tree WorkRead the guide →When to Prune Trees in OttawaRead the guide →

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