Warning Signs Your Tree Is a Hazard Before the High Winds Hit

Key Takeaways

• Early Detection Saves Money: Identifying a hazard before it falls prevents catastrophic property damage and emergency removal fees.
• Ground-Level Red Flags: Mushrooms or heaving soil at the base often indicate root rot that isn’t visible in the canopy.
• The V vs. U Rule: Narrow, V-shaped unions between trunks are far more likely to split than wide, U-shaped ones.
• Deadwood Danger: Brittle, bark-less branches become unguided missiles during 60+ mph Front Range gusts.
• Professional Assessment: An ISA-accredited arborist can identify silent hazards that look healthy to the untrained eye.

In Boulder County, CO, wind isn’t just a weather pattern; it’s a high-stakes structural stress test for every tree on your property. From the notorious Chinook winds that roar off the Front Range to the sudden microbursts of a summer thunderstorm, our trees face forces that can exceed 80 or even 100 mph. While a healthy tree is a marvel of biological engineering designed to flex and sway, a hazard tree is a ticking time bomb waiting for the next atmospheric trigger.

A tree is considered a hazard when it has a structural defect that makes failure likely and is located near a target—such as a home, car, or power line—that it could strike. Because Colorado’s semi-arid climate is so demanding, trees here often suffer from internal stresses, such as drought-induced brittle wood or root systems compromised by rocky soil, that aren’t immediately obvious to the casual observer. Before the next high-wind warning is issued for Lafayette, Louisville, or Boulder, take a proactive walk around your property to identify these ten critical warning signs.

Here are the top 10 warning signs your tree could be dangerous in high winds!

1. The Sudden, Unexplained Lean

Not all leaning trees are dangerous. Some grow at an angle naturally as they reach for sunlight. These trees usually have a curved trunk that shows they have adjusted over time.

The concern is when a straight tree begins to lean, or when an existing lean becomes more noticeable over a short period. This often means the root system is failing.

Check the ground around the base. If the soil is raised, cracked, or shifting, the roots are pulling out of the ground. At that point, the tree is unstable and can fall with very little additional force.

2. Deep Vertical Cracks and Included Bark

Vertical cracks in the trunk or main branches are a clear sign of structural weakness. These cracks often develop where two trunks grow from the same point.

In many cases, bark gets trapped between those trunks. This is called included bark. Instead of forming a strong connection, the tree creates a weak joint that can split under pressure.

When wind pushes against the canopy, these weak points act like fault lines. The tree can split suddenly, especially during storms.

3. Fungi, Conks, or Mushrooms at the Base

Mushrooms growing at the base of a tree or along the trunk are a sign of internal decay. These fungi feed on the wood that gives the tree its strength.

By the time mushrooms appear, the damage inside is often already advanced. The tree may still look healthy from the outside, but the internal structure can be severely weakened.

This type of decay affects the tree’s ability to stay anchored and upright. During strong winds, the tree can fail at the base.

4. Cavities, Hollows, and Nesting Holes

Large holes in the trunk are often viewed as charming habitats for squirrels or birds, but they are major structural liabilities. Cavities are usually the result of an old injury that the tree failed to seal properly, leading to internal decay. While a tree can survive with some internal hollowing, a general rule in arboriculture is that if more than 30% to 40% of the trunk’s diameter is hollow, the tree’s shell no longer has sufficient mechanical strength to support the canopy’s weight during a storm.

5. Deadwood and Hanging Widow-makers

Dead branches are brittle, have no flexibility, and are no longer held firmly by the tree’s living tissue. In the industry, these are called widow-makers because they tend to fall without warning. In a Colorado windstorm, these branches can break off and turn into dangerous debris. If you see limbs without bark, no leaves during the summer, or branches hanging loosely in the upper canopy, they should be removed before they fall on their own.

6. Narrow V-Shaped Unions vs. Wide U-Shaped Unions

The shape of how branches connect to the trunk plays a big role in overall strength. A wide, U-shaped union forms a solid connection, allowing the tree to grow strong supporting wood around the joint. This helps the tree handle movement, weight, and wind without failing.

A narrow, V-shaped union is much weaker. These tight angles do not form the same strong connection and often trap moisture and debris over time. This can lead to internal decay right at the point where the tree needs the most support.

As the tree grows, the pressure between these stems increases, especially in larger trees. During strong winds or heavy loads like snow, this weak connection can split suddenly, often down the center of the tree, leading to major structural failure.

7. Cankers and Missing Patches of Bark

A canker is a damaged area on a branch or trunk where the bark and underlying tissue have died, usually due to disease. It often appears as a sunken, cracked, or discolored section.

When a canker spreads around a large portion of the trunk, it can block the flow of nutrients through the tree. This weakens the tree over time and affects its ability to stay healthy.

The wood beneath a canker is often dry and brittle. If a large canker is located on the main trunk or a major limb, it creates a weak point. Under wind pressure, this area is more likely to crack or snap, leading to failure.

8. The Lion’s Tail Canopy (Over-Pruning)

Ironically, poor maintenance can create a hazard. Lion-tailing occurs when an amateur trimmer removes all the interior branches, leaving foliage only at the very ends of the limbs. This shifts the tree’s center of gravity and prevents the wind from being broken up as it passes through the canopy. Instead, the limbs act like long levers, putting immense pressure on the trunk. In high winds, these branches whip violently back and forth, leading to pendulum failure at the union.

9. Recent Root Zone Disturbance

If you’ve recently done construction, added a driveway, or dug for utilities near a tree, you may have damaged its main support roots. Most of a tree’s stabilizing roots are located in the top 18 inches of soil, so even light digging within the dripline, the area under the outer canopy, can weaken its foundation.

The tree may still look stable, but without those roots, it has lost its support. It might hold up in calm conditions, but under strong winds, it can fail quickly.

10. Premature Fall Color and Canopy Dieback

A tree that turns yellow or drops its leaves in August while its neighbors are still vibrant green is a tree in distress. This early fall is often a sign of root failure or systemic disease. Stressed wood is far less flexible than healthy wood. While a healthy tree can absorb the energy of the wind through flexibility, a stressed, brittle tree will shatter. If the top third of your canopy is bare (dieback), the tree is diverting resources to survive and is likely structurally compromised.

Frequently Asked Questions by Homeowners in Colorado

Can you handle emergency tree removal in Boulder, Colorado?

Absolutely. Roots Up Tree Company provides 24/7 emergency response. We prioritize situations where a tree is leaning toward a structure or blocking access to your property after a storm.

What is the benefit of hiring an ISA-accredited arborist?

An ISA-accredited arborist has passed rigorous testing on tree biology, safety, and proper pruning techniques. This ensures your tree care is based on science rather than guesswork, reducing the risk of future failure.

Can a leaning tree be straightened?

Usually, no. Once a mature tree begins to lean due to root failure, it cannot be safely pushed back. The best course of action is almost always removal to prevent a catastrophic fall.

Does tree cabling really work for support?

Professional cabling and bracing can be highly effective for stabilizing trees with co-dominant trunks or V-unions. It provides a safety net that limits the movement of the stems during high winds.

How often should I have my trees inspected?

In the Front Range, we recommend a professional inspection every 2–3 years, or immediately after a major weather event like a heavy spring snow or a high-wind storm.

Summary Checklist: Pre-Storm Hazard Audit

Final Advice

To determine if your tree is a hazard before high winds hit, you must look for structural red flags like vertical trunk cracks, shelf mushrooms at the base, and tight V-shaped unions, which are the most common points of failure during a Colorado windstorm.

• If you notice a sudden lean accompanied by heaving soil, the tree is in the process of uprooting and requires immediate, professional intervention to protect your home.
• Don’t be fooled by a green canopy; many trees that look healthy on the outside are structurally hollow or suffering from severed root systems that provide no stability against 80-mph gusts.
• By conducting a pre-storm audit and identifying these ten warning signs early, you can choose a controlled, safe removal over a chaotic, expensive emergency.
• Remember that preventative maintenance, such as thinning the canopy to reduce wind resistance or installing cables to support weak limbs, is always more cost-effective than repairing a crushed roof.
• For the safety of your family and property, always rely on an ISA-accredited arborist to evaluate trees near your home, as they have the tools to see the internal decay that the human eye misses.

Protecting your home from the unpredictable power of Colorado’s high winds requires a team that combines scientific precision with decades of local experience. Roots Up Tree Company is your dedicated partner in Boulder County, offering high-quality and affordable tree services designed to identify and eliminate hazards before they become emergencies. Based in Lafayette and serving the entire region from Longmont to Broomfield, our family-owned and locally-operated team brings over 45 years of combined experience in technical tree removal and hazard mitigation. 

Reviewed by a Certified Arborist

This article has been reviewed by a certified arborist to ensure all information regarding tree care and storm safety is accurate and up to industry standards.