Most trees are not dangerous. But some are, and the problem is that a hazardous tree does not always look obviously sick or damaged from the outside. Knowing what to look for can help you identify a tree that poses a genuine risk to your home, your family, or your neighbors before something goes wrong.
This guide covers the warning signs of a hazardous tree, when to call a professional, and what your options are once a problem is identified.
What Makes a Tree a Hazard?
A hazard tree is any tree with a structural defect, disease, or condition that increases the likelihood of it failing, either fully or partially, in a way that could cause harm or property damage. Hazard trees do not need to be dead or visibly diseased to pose a risk. A structurally compromised but otherwise healthy-looking tree can fail just as catastrophically as a dead one.
The risk level of a hazard tree depends on two factors: the likelihood of failure and the consequences if it does fail. A large tree with a significant defect directly over your roof is a much higher priority than the same defect in a tree at the back of a wooded lot away from any structures.
Warning Signs That a Tree May Be a Hazard
Leaning
A tree that has developed a noticeable lean, especially one that has changed angle recently, is a significant warning sign. A gradual lean that has been present since the tree was young is less concerning than a lean that has developed suddenly or has worsened after a storm.
Check the base of a leaning tree for soil heaving or cracking on the opposite side of the lean. This indicates that the root system is starting to pull out of the ground, which is a serious structural failure in progress.
Cracks and Splits in the Trunk
Deep cracks running vertically along the trunk, or cracks that pass through the wood rather than just the bark, indicate serious structural weakness. A crack at the junction where a large branch meets the trunk is particularly dangerous because it can fail suddenly under wind load or the weight of ice.
Codominant Stems
A codominant stem structure occurs when two or more main stems of similar size grow from the same point on the trunk. The junction between codominant stems often contains included bark, which is bark that has grown into the union rather than wood-to-wood contact. Included bark creates an inherently weak attachment point that is prone to splitting, sometimes catastrophically and without warning.
Look for a V-shaped or very narrow angle between two main stems. A wide, U-shaped angle is generally stronger. A tight V, especially with visible bark in the crease, is a red flag.
Decay and Cavities
Soft, spongy wood, hollow sections, or visible cavities in the trunk or major branches all indicate internal decay. Decay weakens the structural integrity of the wood from the inside, which means the tree can look relatively normal on the outside while being significantly compromised internally.
Some surface decay is visible as discoloration, soft spots, or crumbling bark. But internal decay is not always obvious without a professional assessment. If you tap on a section of the trunk and it sounds hollow, that is worth having evaluated.
Fungal Growth
Mushrooms, conks, or shelf fungi growing at the base of a tree, on the trunk, or at the root flare are a reliable sign of internal decay. Fungal growth indicates that wood-rotting organisms are active inside the tree, breaking down the structural tissue.
A single mushroom near the base is not necessarily an emergency, but multiple fruiting bodies, large conks, or fungal growth at multiple points on the tree warrant a professional evaluation.
Dead Branches
Dead branches, sometimes called widowmakers, are a hazard even on an otherwise healthy tree. Dead wood is more brittle than live wood and more likely to break and fall, particularly during wind or ice storms. A tree with significant dead wood throughout the canopy, which has a “lion’s tail” appearance when only the branch tips have foliage, needs attention.
Root Damage or Decay
Root problems are harder to spot than above-ground defects, but they are just as dangerous because they compromise the tree’s ability to stay upright. Look for:
- Soil heaving or cracking around the base of the tree
- Mushrooms or fungal growth at the root flare
- Roots that have been cut or damaged by construction, trenching, or paving
- A general decline in canopy health without an obvious above-ground cause
Construction activity within the root zone is a common cause of hidden root damage that does not show up in the canopy for several years after the initial injury.
Previous Storm Damage
Trees that have survived major storms can have internal damage that is not immediately visible. Split wounds that have partially closed, large sections of removed canopy that shifted the tree’s weight distribution, and wounds that were never properly cleaned up can all create structural vulnerabilities that only become apparent years later.
If a tree on your property went through a significant storm event and you never had it evaluated afterward, it is worth scheduling a professional assessment.
When to Call a Professional Immediately
Some situations should not wait. Call a tree service right away if:
- A tree or large branch is actively leaning toward your home, a neighboring structure, or a power line
- You can see soil lifting or cracking at the base of a tree after a storm
- A large branch has partially failed and is hanging or wedged in the canopy
- A tree has cracked at the trunk or a major branch following a storm
- You can see a cavity or hollow section in the trunk of a tree near your home
These are situations where the risk of waiting outweighs the cost of acting quickly.
What Are Your Options Once a Hazard Tree Is Identified?
Not every hazard tree needs to come down. Depending on the nature and severity of the defect, a certified arborist may recommend one of several approaches.
- Pruning: Removing dead wood, reducing the weight of specific branches, or eliminating a problematic codominant stem can significantly reduce the risk of a tree without removing it entirely.
- Cabling and bracing: Supplemental support systems can be installed in the canopy to reduce the load on weak unions or codominant stems. This is not a permanent fix, but it can extend the safe life of a tree that is worth preserving.
- Regular monitoring: Some defects are stable and do not require immediate action, but should be monitored over time. A certified arborist can establish a monitoring schedule and let you know if conditions change.
- Removal: When a defect is severe, the tree is in an unavoidable target zone, or the tree is too far declined to respond to treatment, removal is the safest option.
The Value of a Professional Tree Risk Assessment
A DIY inspection can help you identify obvious warning signs, but many hazardous tree defects require trained eyes and specialized equipment to detect. A certified arborist conducting a formal tree risk assessment uses a structured methodology to evaluate the likelihood and consequences of failure, which gives you a defensible, documented assessment rather than a guess.
This documentation also matters if a tree has been identified as hazardous and you need to demonstrate to an HOA or insurance company that you took appropriate action.
ADM Tree Services, LLC offers professional tree risk assessments throughout Northern Virginia. If you have a tree you are concerned about, do not wait for a storm to find out whether your instincts were right.
Frequently Asked Questions
In Virginia, each property owner is generally responsible for damage that occurs on their own property. However, if you were notified of a hazardous tree and failed to act, you may be held liable for resulting damage. Written documentation of any notification matters in these situations.
Yes. Internal decay, root damage, and structural defects, such as included bark in codominant stems, are not always visible from the outside. A tree can appear outwardly healthy while being significantly compromised internally.
For trees near structures or high-traffic areas, a professional assessment every three to five years is a reasonable baseline. After a major storm, any trees that may have sustained damage should be evaluated promptly.
Get a Tree Risk Assessment in Northern Virginia
ADM Tree Services, LLC serves homeowners and businesses across Northern Virginia. Call (703) 771-8080 or fill out our online contact form to schedule a tree risk assessment or request a free estimate.
