How to Spot a Hazardous Tree — 10 Warning Signs Every Pennsylvania Homeowner Should Know

Most trees that fail catastrophically gave visible warning signs for months or years before they fell. The problem is that most homeowners do not know what to look for. This guide covers the ten most important warning signs of a hazardous tree — things you can assess from the ground during a walk around your property. Any one of these signs warrants a professional evaluation; multiple signs mean the situation is urgent.

Sign 1: Significant Lean That Is Getting Worse

Many trees have a natural lean — this is not automatically a problem. What matters is whether the lean is stable or increasing. A tree that has leaned the same direction for decades with healthy root structure may be fine. A tree that has developed a new lean, or whose lean has measurably increased over a season, is telling you its root system or trunk structure is failing.

How to check: take a photograph from the same position each year in late winter (no leaves to obscure the outline). Compare over time. Increasing lean — even slowly — is a serious warning sign.

Sign 2: Soil Heaving or Lifting at the Base

If you can see the soil around the base of a tree lifting or separating from the normal ground level on one side, the tree’s root plate is beginning to fail. This is particularly visible on the side opposite the lean direction — as the tree tips one way, the root plate on the opposite side lifts. This is one of the most urgent warning signs — a tree in this condition can complete its fall in the next wind event.

Sign 3: Cracks or Splits in the Trunk

Vertical cracks running along the trunk are a significant warning. Cracks indicate that the wood is under tension or compression stress beyond its capacity to hold. Look for:

• Vertical cracks running along the trunk for more than a foot
• Open cracks where you can see into the interior of the trunk
• Frost cracks — vertical splits that appear or worsen in late winter after freeze-thaw cycles
• Horizontal seams around the base, which can indicate basal decay

Sign 4: Cavities or Hollow Sections in the Trunk

A visible cavity in the trunk — an opening into the tree’s interior — indicates that decay has removed structural wood. The question is how much structural wood remains. As a general rule used by arborists: if the combined wall thickness of sound wood around a cavity is less than 30–40% of the tree’s total diameter at that point, structural integrity is significantly compromised. A pencil-sized hole is not a crisis; a cavity you could fit your hand into warrants evaluation.

Sign 5: Fungal Fruiting Bodies (Conks, Mushrooms)

Any fungal growth on the trunk, at the base, or on major roots indicates active wood decay. Key species to recognize in the Lehigh Valley:

• Ganoderma (artist’s conk): Large shelf-shaped conk, brown or red-brown on top, white pored underside. Indicates significant heartwood decay.
• Armillaria (honey mushrooms): Clusters of small honey-colored mushrooms appearing at the base in fall. Indicates root rot — one of the most dangerous decay types for structural stability.
• Chicken-of-the-woods (Laetiporus): Bright orange and yellow shelf fungus. Indicates significant heartwood decay in oaks and other hardwoods.

Important: the visible mushroom or conk is just the fruiting body. The actual fungal mycelium has been growing through the wood for years before the fruiting body appears. Fruiting bodies are a late-stage indicator of an established decay problem, not an early warning.

Sign 6: Codominant Stems with Included Bark

When a tree grows two main trunks from a single point (codominant stems), the junction between them can be either strong or weak depending on the bark structure at that point. “Included bark” — bark that grows inward between the stems rather than out from them — creates a V-shaped notch at the stem junction and significantly weakens the attachment. Push the two stems slightly apart and look: if you see bark inside the V rather than a smooth flare of wood, you have included bark, and this union is a high-risk failure point under ice or snow load.

Sign 7: Dieback in the Crown

Dead branches in a tree’s canopy are normal at low levels — some branch shedding is part of every tree’s natural growth pattern. But significant dieback — 30% or more of the canopy showing dead branches — indicates serious stress. Look for:

• Dead branches persisting in the canopy through multiple seasons (should have shed naturally)
• Sections of the crown that have no leaves while the rest of the tree is leafed out
• Progressive dieback moving from the top of the crown downward (known as “dieback from the tips” — a sign of root stress, vascular disease, or systematic decline)

Sign 8: Recent Storm Damage Not Cleaned Up

A tree that has sustained storm damage — broken large branches, splits, or partial uprooting — and had that damage left unaddressed is more hazardous than before the storm. Broken branch stubs left in the tree decay faster than proper pruning cuts, introduce disease, and create attachment points that are structurally weaker than the original branch union. A post-storm assessment and cleanup is not optional for trees near structures — it is risk management.

Sign 9: Construction Damage to Root Zone

Trees that have had significant construction activity within their root zone — trenching for utilities, soil compaction from machinery, grade changes that buried the root flare — may look healthy for 2–5 years before showing decline. The damage to the root system is not immediately apparent in the canopy. If you know a tree near your home had construction activity in the past few years, it warrants monitoring for delayed decline symptoms.

Sign 10: Pest or Disease Indicators for Local Species

Several active pests and diseases in the Lehigh Valley can cause rapid structural decline:

• Emerald Ash Borer: S-shaped galleries under bark, D-shaped exit holes, upper-crown dieback, heavy bark woodpecker activity (birds excavating for EAB larvae). Any ash tree showing these signs is at or near total mortality.
• Spotted Lanternfly: While SLF does not directly kill most trees (tree of heaven excepted), heavy infestations weaken hosts over multiple years. Grapevines, hops, and tree of heaven die quickly; maples, oaks, and other hosts suffer chronic stress.
• Beech Leaf Disease: Dark striping between leaf veins (visible from below the leaf against the light), early leaf drop, crown thinning. This disease has been spreading rapidly through Northampton County beech populations since 2022.

What to Do If You Identify Warning Signs

For any combination of two or more of the signs above on the same tree, contact a licensed, insured arborist for a professional hazard assessment. A professional assessment will:

• Rate the probability of failure under specified conditions (normal weather, high wind, ice load)
• Identify the specific failure mode (trunk crack, root failure, structural defect)
• Rate the consequence of failure (what is in the target zone if the tree fails)
• Recommend risk mitigation options: monitoring, pruning, cabling, or removal

A written assessment also protects you legally — if you have documented that you identified and addressed a hazardous tree, you have evidence of reasonable care as a property owner.

Stone Ridge Landscaping LLC provides professional tree hazard assessments and removal throughout Lehigh and Northampton Counties. If a tree concerns you, call us — an honest evaluation costs nothing and could prevent an expensive emergency later.