7 Signs a Tree Is a Hazard and Needs to Come Down (Rochester)

By Daniel Reyes, Tree Care & Risk. Last updated: July 22, 2026

Most homeowners in Monroe County can point at the tree that worries them: the big silver maple over the Penfield driveway, the leaning oak by the Brighton fence, the bare ash out back in Greece. What they usually cannot do is read whether that tree is a genuine hazard or just an ordinary old tree with cosmetic quirks. This is a field checklist for that read. It walks through the concrete signs that actually predict failure, why Rochester's ice load and emerald ash borer make some of them urgent, and how a professional turns a sign into a decision.

What makes a tree a hazard rather than just a defect?

A tree is a hazard only when a part likely to fail lines up with a target it could damage, so arborists score risk as the likelihood of failure multiplied by the likelihood of striking a target and the consequences if it does. The International Society of Arboriculture frames tree risk exactly that way through its Tree Risk Assessment Qualification (TRAQ) program. A dead limb over an empty back field is trivial. The same limb over a bedroom is an emergency, and that is the whole point of condition times target.

The stakes are not abstract. In a study published in the journal Natural Hazards, geographer Thomas Schmidlin of Kent State University counted 407 people killed by wind-related tree failures in the United States from 1995 to 2007, an average near 31 deaths a year, with snow and ice driving a small share (3%) of them. Upstate New York supplies plenty of both wind and ice, which is why a stable-looking tree with a hidden defect deserves more than a glance. If you want the full methodology behind how professionals score all of this, our explainer on what a formal tree risk assessment covers breaks it down.

Is the canopy full of dead or hanging limbs?

Dead, broken, and hanging limbs are the most common failure point and the easiest sign to read from the ground. A scatter of small deadwood is normal on any mature tree. Large dead branches, a limb snapped and lodged in the crown (a hung-up widowmaker), or a canopy that is more than a quarter dead signals a tree shedding weight it can no longer support. Over a patio, a driveway, or a sidewalk, that is a target waiting for the next storm.

The share of dead canopy is a useful threshold. Purdue University's extension arborists advise that once a tree has lost more than 30% of its canopy, owners should plan to remove it, because decline at that stage rarely reverses. Hanging and broken limbs also do not wait for a gale: they come down in ordinary wind, under wet snow, or on a calm afternoon. Keep people and cars out from under a crown that is visibly failing until it can be cleared.

Do cracks, splits, and included bark signal a failing trunk?

The trunk and its main unions carry the entire tree, so a failure there tends to be catastrophic rather than the loss of a single branch. Look for a deep vertical crack running up the stem, a seam where bark has split and not resealed, and included bark: dark, inrolled bark trapped between two codominant stems that grew up in a tight V. A tree that forks into two equal trunks off a narrow union is structurally weaker than one with a single dominant leader.

Included bark matters most in our climate because it fails under load. A V-shaped union with bark trapped inside has no continuous wood tying the two stems together, so an ice storm or a heavy wet snow can split the tree straight down the middle. Deep frost cracks and old split seams behave the same way. If you are seeing new bark splitting and cracking on a trunk, treat it as a structural signal rather than a cosmetic one, especially on a large tree near the house.

Is the tree leaning with heaving or lifted roots?

A lean the tree grew with over decades is usually stable, but a lean that appeared suddenly is a failure already in progress. The tell is at the base. Cracked or mounded soil on one side of the trunk, or roots lifting out of the lawn, means the root plate is tearing loose from the ground. That is different from an old, settled lean where the soil around the flare is undisturbed and the tree has adjusted its wood to cope.

Rochester's soils make this worse than in many regions. Our heavy clay and glacial till hold water after wet springs and during snowmelt, and saturated ground loses its grip on a root system. A tree that leaned overnight after a storm, with fresh soil heave on the upwind side, can come down with no further warning. If you see that combination, keep people and vehicles out of the fall zone and get it evaluated fast, rather than waiting to see whether it settles.

Do fungal conks or a hollow trunk mean the wood is rotting?

Shelf-like conks or clustered mushrooms on the trunk or root flare often mean decay fungi are consuming the structural wood from the inside, and a cavity or hollow you can reach a hand into confirms that the load-bearing shell is thinning. A decaying tree can look green and full in the canopy while the column holding it up quietly fails. Not every fungus is a death sentence, but fruiting bodies low on a large tree over a target always warrant a professional look.

Location and type do the diagnosing. A mushroom in surface mulch is a decomposer doing its job. A firm, perennial conk emerging from the root flare or the lower trunk points to root or butt rot inside the wood, which reduces the tree's ability to stand. Because the outside can look fine, this is one of the harder signs for a homeowner to weigh, so our guide to mushrooms and conks at the base of a tree explains which ones justify concern.

Why are EAB-killed ash trees an urgent hazard in Monroe County?

Emerald ash borer has killed hundreds of millions of ash across North America since it was found in 2002, and a dead ash is uniquely dangerous because it turns brittle fast and drops limbs without warning. The beetle's larvae girdle the thin band of water-conducting tissue just under the bark, so the wood dries out and snaps rather than bending the way a live limb does. In Monroe County, a standing dead ash near the house is a remove-while-it-is-safe situation, not a wait-and-see one.

The timeline is faster than most people expect. Purdue's extension arborists note that an ash tree's structural integrity can begin to decline while the tree is still mostly green with roughly two-thirds of its canopy intact, and that it is not uncommon for sizable limbs to snap 30 feet off the ground on a calm, clear day. Many crews will not climb an ash that has been dead more than a few months, which means waiting drives the eventual removal toward a crane and a bigger bill. If your ash is only beginning to show borer damage, the treat-versus-remove decision for an infested ash is worth making now, and our overview of emerald ash borer in Monroe County covers what the infestation looks like locally.

Do root damage and site history change the risk?

Roots anchor the tree and are the hardest defect to see, so recent digging, trenching, driveway or foundation work, and chronic wet soil all raise the odds of failure even on a tree that looks healthy from the crown down. A tree that lost anchoring roots to a utility trench three years ago can fail long after the disturbance, once decay finishes the job. Site history is part of the read, not a footnote to it.

Two root problems are worth naming. Girdling roots that circle and compress the trunk slowly strangle a tree, and a root flare buried under piled soil or a mulch volcano hides decay and keeps the base wet. Some of this is correctable: girdling roots caught early can sometimes be addressed through root collar excavation, which can keep a borderline tree standing. Widespread root loss or advanced root rot, by contrast, removes the anchoring the tree depends on and points toward removal.

How do you turn a hazard sign into a decision?

Spotting a sign tells you a tree needs attention, but it does not tell you the probability of failure or the right fix. A TRAQ-qualified arborist scores each defect against its specific target, then recommends the least-invasive option that manages the risk: prune the deadwood, cable a weak union, monitor a stable lean, or remove only what cannot be corrected. That is the difference between a documented rating and a guess made from the driveway.

The written assessment also protects you. Under New York law, a property owner who knew or reasonably should have known a tree was hazardous can be held responsible if it fails and causes harm, so a dated report from a qualified arborist is evidence that you acted reasonably, which matters for both safety and insurance. If a storm just damaged the tree, our notes on handling a storm- or lightning-struck tree cover the immediate steps, and our guide to when a tree actually needs to be removed walks through the cut-versus-save line in more detail.

FAQ

Does a dead ash tree have to be removed right away?

A standing dead ash near a house, driveway, or walkway should be removed promptly rather than left to stand. Ash killed by emerald ash borer becomes brittle fast and can shed large limbs in light wind or even calm weather, and many crews will not climb one that has been dead more than a few months, which pushes the job toward costlier crane work the longer you wait.

Are mushrooms at the base of a tree always a hazard sign?

No. A mushroom in surface mulch or on a dead stump is usually a harmless decomposer. The concern is a firm, shelf-like conk emerging from the root flare or lower trunk, which can indicate decay fungi hollowing the structural wood from the inside. Because a decayed tree can still look green on top, the type and location of the fungus should be assessed by an arborist.

Is a leaning tree always dangerous?

Not always. A tree that grew at an angle over many years, with undisturbed soil around the base, is often stable and may only need monitoring. A tree that leaned suddenly, especially with cracked or mounded soil and roots lifting on one side, has a failing root plate and can come down without warning. The sudden lean is the emergency, not the long-standing one.

What is included bark, and why does it make a tree hazardous?

Included bark is bark that becomes trapped between two stems or branches that grew up in a tight V-shaped union. Because there is no continuous wood binding the stems together, the union is weak and prone to splitting under the ice, wet snow, and wind load common in Upstate New York. Codominant stems with included bark are a frequent cause of whole-tree and large-limb failure.

Can I judge how risky a tree is on my own?

You can spot most of the visible signs: dead limbs, cracks, a fresh lean, basal conks, and a buried or damaged root flare. What you generally cannot judge is the internal extent of decay or the true probability of failure, which is where a TRAQ-qualified arborist adds value by scoring the defect against its target and documenting the result.

Sources

• Monster Tree Service of Rochester
• International Society of Arboriculture (ISA): Recognizing Tree Risk
• USDA APHIS: Emerald Ash Borer
• Purdue Landscape Report: Avoid the Deadly Risk of Dying Ash Trees
• Schmidlin, T.W. (2009). Human fatalities from wind-related tree failures, Natural Hazards
• NYS Department of Environmental Conservation: Forests & Trees