Is That Crack in My Tree Dangerous? How a Montgomery County Arborist Tells the Difference

You walk out to the yard, look up at a tree you have passed a thousand times, and notice something new: a crack running down the trunk. Maybe it is a thin vertical line, maybe it is a deep split where two big stems meet. The question every homeowner asks next is the right one: is that crack dangerous, or is it nothing to worry about?

The honest answer is that it depends. Some cracks are normal and harmless. Others are a structural warning that a tree could fail in the next storm. As local arborists serving Rockville, Bethesda, Potomac, Silver Spring, Kensington and the rest of Montgomery County, MD, we inspect cracked trees every week. Here is how we tell the difference, and how you can do a first read on your own tree before deciding whether to call a professional.

Why cracks matter so much

A tree trunk is the structural backbone that holds the entire canopy up against wind and gravity. When a crack forms, it interrupts the continuous wood fibers that give the trunk its strength. According to the Tree Care Industry Association, a cracked or rotted tree can fail under its own weight, and it does not always take a storm or high wind to bring it down (TCIA).

That risk is amplified here in Montgomery County. Our trees face a punishing cycle of summer thunderstorms, saturated clay soil, freeze-thaw winters, and the occasional ice storm. We saw the consequences in June, when fast-moving storms brought down dozens of trees across the county. A trunk with an existing crack has far less margin to survive that kind of weather.

Not every crack is an emergency

Before you panic, understand that trees crack as a normal part of growing. Bark splits and minor surface cracks happen as a tree expands over many seasons, and many of these never cause a problem. The University of Florida notes that some natural cracks on a lower trunk are normal for certain species and may cause no issues at all, though they can also be the starting point for a failure later (University of Florida).

So the goal is not to fear every crack. The goal is to learn which cracks are cosmetic and which ones signal a structural defect. Below are the cracks that genuinely concern us.

The cracks that worry an arborist

1. Deep vertical cracks in the main trunk

A deep, vertical crack or seam running down the main trunk is a serious sign. It means the wood fibers that carry the load have separated. The deeper and longer the crack, the weaker the trunk. If you can fit a coin or your fingers into the crack, or if you see two faces of wood that have clearly pulled apart, treat it as a red flag and have it inspected.

2. Splits where two large stems meet (codominant stems)

One of the most common and most dangerous defects we see is a split where the trunk forks into two large stems of roughly equal size. These are called codominant stems, and research has shown that a forked junction is only about half as strong as a solid trunk (Bartlett Tree Experts).

Often these junctions hide what arborists call included bark, where bark grows trapped inside the union instead of the two stems properly bonding together. Included bark is one of the leading causes of sudden, split-second tree failure, because the union can pull apart without much warning in high wind, heavy snow, or even under the chronic pull of gravity (Florida Urban Forestry Council). If you see a tight V-shaped fork with a crack starting at the bottom of the V, that tree needs professional eyes on it.

3. A crack paired with a new or worsening lean

A crack on its own is concerning. A crack combined with a tree that has recently started leaning is a near-emergency. The lean tells us the tree is already under abnormal load, and the crack tells us the structure is giving way. Look for cracked or heaving soil at the base on the side opposite the lean, which can mean the roots are lifting.

4. Cracks with signs of decay, fungus, or hollowing

A crack becomes far more dangerous when it is paired with decay. Water enters a crack, fungi follow, and the wood inside begins to rot and hollow out. Look for mushrooms or shelf-like fungus growing on the trunk or at the base, soft or crumbling wood, sawdust at the base, or a hollow sound when you tap the trunk. A crack on a decayed trunk has almost no remaining strength.

5. Cracks under or near large branches

Cracks that appear directly under a heavy branch, or at the point where a large limb attaches to the trunk, are especially risky. The University of Florida specifically warns that cracks under branches can create dangerous conditions, because that is exactly where the load concentrates.

Cracks that are usually less serious

Not every crack means removal. A few are common and frequently harmless, though they still deserve monitoring:

• Frost cracks. These are vertical splits that form in late winter to early spring, usually on the south or southwest side of the trunk where the sun heats the bark and then a sudden temperature drop makes the wood contract (Missouri Botanical Garden). They are common on thin-barked trees in our Maryland winters. Many frost cracks seal over, but they can become an entry point for decay, so keep an eye on them.
• Shallow bark splits. Surface-level splits in the outer bark, with sound wood underneath, are often just the tree growing. Watch them, but they are rarely an immediate hazard.
• Old, sealed cracks. A crack that has rolled over with healthy callus wood on both edges is one the tree has been managing. These should still be checked if they are large, but they are usually more stable than a fresh, open crack.

The key with any of these is whether they are stable or changing. A crack that is getting longer, wider, or deeper over time is moving in the wrong direction.

A simple at-home check

You do not need to be an arborist to do a first assessment. Walk around the entire tree and ask yourself:

• How deep and long is the crack? Surface bark, or into the solid wood?
• Is it on the main trunk, or where two large stems fork?
• Is the tree leaning, and is there cracked or heaving soil at the base?
• Do you see fungus, soft wood, sawdust, or hollow areas near the crack?
• Is there a house, driveway, deck, play area, car, or power line within the fall zone?
• Has the crack changed since you last looked?

If the crack is deep, located at a fork, paired with a lean or decay, or sits above something you care about, do not wait. That combination is exactly what we see on trees that fail.

Why the target matters in Montgomery County

Arborists assess risk as a combination of the likelihood a tree will fail and what it would hit if it did. A cracked tree in the middle of an open field is a low priority. The same cracked tree leaning over a bedroom, a driveway, or a sidewalk in a neighborhood like Rockville, Bethesda, or Silver Spring is a different conversation entirely.

Because so many Montgomery County homes sit close to mature trees, the fall zone almost always includes something valuable. That is why we treat trunk cracks near structures with urgency rather than a wait-and-see approach.

Can a cracked tree be saved?

Sometimes, yes. Depending on the location and severity, an arborist may be able to support a tree with structural cabling or bracing, reduce the weight of the canopy through pruning to lower the load on a weak point, or simply monitor a stable, minor crack over time. These are real options for trees that are otherwise healthy and have a defect that can be managed.

But some cracks are past saving. A trunk with a deep, active split, a failing codominant union with included bark, or a crack combined with significant decay often cannot be made safe, and removal is the responsible choice. The right call depends on a hands-on inspection, not a guess from the ground.

When to call a professional

Maryland law requires that anyone performing tree care work for hire on trees over 20 feet be a Licensed Tree Expert, and for good reason. Assessing a cracked trunk and deciding whether to cable it, prune it, or remove it involves real risk to people and property. This is not a DIY project, especially when the tree is near your home or power lines.

At Rock Creek Tree, Turf & Landscape, we provide on-site inspections for cracked and damaged trees throughout Montgomery County. If you have noticed a crack and you are not sure how serious it is, we will tell you honestly: monitor it, support it, or remove it. If a tree is an immediate hazard over your home, our emergency tree service can respond quickly.

Not sure about a crack you spotted? Request a free quote and we will take a look before the next storm does.

Frequently asked questions

Is a crack in a tree trunk always dangerous?

No. Some cracks are shallow bark splits or natural growth cracks that cause no problem. The dangerous ones are deep vertical cracks in the main trunk, splits at a fork between two large stems, and any crack paired with a lean, decay, or fungus. Depth, location, and whether the crack is changing are what matter most.

What is the difference between a frost crack and a structural crack?

A frost crack forms in late winter and early spring, usually on the south or southwest side of the trunk, when sun warms the bark and a sudden temperature drop makes the wood contract. Many frost cracks seal over. A structural crack reflects the trunk actually pulling apart under load and is far more likely to lead to failure, especially at a forked union or alongside a lean.

My tree forks into two trunks with a crack at the base. Should I worry?

Yes, this deserves prompt attention. Forks of two similar-sized stems, known as codominant stems, are only about half as strong as a single trunk, and they often hide included bark that can split suddenly in a storm. A crack starting at the bottom of that V is a classic warning sign and should be inspected by a Licensed Tree Expert.

Can you fix a cracked tree instead of removing it?

Sometimes. For otherwise healthy trees, cabling and bracing, weight-reduction pruning, or monitoring can manage a defect. But a deep active split, a failing fork with included bark, or a crack combined with major decay often cannot be made safe, and removal is the safer choice. An on-site inspection determines which path makes sense.

How fast can a cracked tree fall?

There is no fixed timeline. A cracked or decayed tree can fail under its own weight on a calm day, or it can stand for years. The danger is that storms accelerate everything. With Montgomery County thunderstorms and saturated soil, a crack that seemed minor can become the failure point overnight. If a crack is serious and sits over something valuable, do not gamble on time.