How to Tell If a Tree Is Dangerous: A Calgary Homeowner’s Safety Guide
Calgary’s weather can be unpredictable. Windstorms, chinooks, heavy snow, drought, and sudden freeze–thaw cycles all put stress on trees. Even healthy-looking trees can hide structural issues that make them hazardous.
At Calgary Tree Care, our ISA Certified and TRAQ Qualified Arborists conduct tree risk assessments across the city. This guide outlines the warning signs that a tree may be unsafe—and why early detection is essential for preventing property damage or injury.
Why Dangerous Trees Are a Serious Concern in Calgary
Calgary’s climate accelerates tree failure due to:
• Strong chinook winds
• Heavy, wet snow loading
• Rapid temperature swings
• Soil heaving and saturation
• Repeated drought cycles
• Old, previously-topped trees
• Urban environments with limited root space
Understanding these factors helps homeowners spot danger before disaster strikes.
1. Cracks in the Trunk or Major Branches
Vertical cracks, open seams, or deep splits significantly weaken a tree’s structure. Even if the tree remains standing, these defects can lead to sudden breakage—especially during windstorms.
Look for:
• Long cracks in the bark
• Sunken or discoloured areas
• Oozing sap from wounds
• Cracks that appear after chinooks or cold snaps
Cracked trunks are one of the most serious risk indicators.
2. Dead or Hanging Branches
Dead limbs—especially large ones—are unpredictable and often fail without warning.
Signs include:
• Brittle branches that snap easily
• No foliage during growing season
• Bark falling off branches
• Partially attached “hangers”
These branches become projectiles in high winds or heavy snow.
3. Sudden or Worsening Lean
A tree that develops a new lean or begins tilting more over time may be experiencing root instability.
Dangerous leans are indicated by:
• Soil cracking or lifting around the trunk
• Exposed roots on one side
• Leaning after storms or strong winds
• A direction of lean toward a home, sidewalk, or driveway
Any sudden posture change should be evaluated immediately.
4. Fungal Growth at the Base of the Tree
Mushrooms, conks, or fungal shelves are signs of internal decay. When a tree shows visible fungus, internal structural strength may already be compromised.
Watch for:
• Shelf-like conks
• Mushrooms growing around the root flare
• Soft or spongy bark near the base
Decay significantly increases failure risk.
5. Hollow or Soft Spots in the Trunk
Hollow trunks or soft areas indicate loss of structural wood. Trees with significant hollows are more likely to fail under wind or snow load.
Common symptoms include:
• Cavities in the trunk
• Hollow sounds when tapped
• Bark that easily dents or compresses
Degree of hollowing can only be accurately assessed by an arborist.
6. Root Damage or Poor Root Health
Roots anchor the tree and absorb water. Damage to the root system is one of the leading causes of sudden tree failure.
Signs of root issues include:
• Fungal growth at soil level
• Soil heaving
• Cracked or uplifted ground
• Construction or excavation nearby
• Sparse foliage in the upper canopy
Root problems are invisible from above ground without signs like these.
7. Excessive Deadwood Throughout the Canopy
Branches dying throughout the canopy indicate systemic health decline. Trees that cannot support their canopy are at increased risk of structural failure.
Common causes include:
• Drought
• Disease
• Insect damage
• Poor soil conditions
• Advanced age
Declining trees should be assessed promptly.
8. Co-Dominant Stems or Weak Branch Unions
Trees with two or more main stems often split where the trunks meet, especially during strong winds.
Indicators include:
• “V” shaped unions instead of wide “U” shapes
• Inward-bark inclusion (bark trapped between stems)
• Cracks forming at the union
These defects are common in poplars, aspens, and ornamental species.
9. Trees Previously Topped
Topping severely weakens trees and often leads to:
• Weak regrowth
• Decay at cut sites
• Structural instability
• Increased risk of breakage
Many older Calgary trees were topped decades ago and are now reaching dangerous maturity.
When a Tree Becomes a Safety Risk
A tree becomes hazardous when it has:
• Significant structural defects
• Root instability
• Large amounts of deadwood
• Trunk cracks or decay
• Severe lean toward targets
• Recent storm or wind damage
Hazardous trees require immediate professional evaluation.
What Homeowners Should Avoid
Do not attempt:
• DIY pruning of large or broken limbs
• Cutting or bracing a leaning tree
• Digging around damaged roots
• Climbing a compromised tree
• Removing storm-damaged branches without proper equipment
Tree risk assessment is highly technical and dangerous without proper training.
How ISA Certified Arborists Assess Risk
A professional assessment includes evaluating:
• Structural soundness
• Species and growth patterns
• Wind exposure
• Soil stability
• Root plate condition
• Previous wounds
• Decay indicators
• Proximity to targets
TRAQ methodology ensures objective, evidence-based recommendations.
Why Choose Calgary Tree Care
Our ISA Certified and TRAQ Qualified Arborists bring more than 15 years of experience assessing dangerous trees in Calgary’s challenging climate. We provide:
• Tree risk assessments
• Hazard mitigation
• Structural pruning
• Cabling and bracing
• Honest removal recommendations when necessary
Safety is always our top priority.
Schedule a Tree Risk Assessment
If you suspect a tree on your property may be dangerous, contact Calgary Tree Care for a professional evaluation. Early detection prevents property damage and ensures your landscape remains safe and healthy.
