Is this you?
- ▸Vertical crack running up or down the trunk for more than 12 inches
- ▸Crack that goes deep into the wood (not just bark)
- ▸Crack that opens and closes with weather or wind
- ▸Water, sap, or staining flowing from the crack
- ▸Two trunks splitting apart at a V-shaped union
- ▸Crack at a branch attachment point
Frost cracks are the most common in Spokane — long vertical splits caused by rapid temperature changes on sunny winter days. South and southwest sides of the trunk freeze and thaw repeatedly, and at some point the bark and outer wood crack. Frost cracks are usually superficial, often re-close in summer, and rarely require removal. They're a cosmetic issue more than a structural one.
Lightning cracks are dramatic — a single long, often spiral, split running from the canopy to the ground. Lightning strikes vaporize the moisture in the cambium layer and blow a strip of bark and wood off the tree. Some lightning-struck trees survive; many don't. The decision tree is: is the crack still actively expanding (failure risk), is the canopy showing dieback (death risk), and is the tree near a target (removal urgency). Most lightning-struck trees we see end up needing removal within 1–3 years.
Structural cracks are the dangerous ones — splits at branch unions, cracks across the grain of the trunk, or vertical cracks that open during wind events. These signal that the wood is mechanically failing in real time. A trunk crack that closes when it's calm and opens when it's windy is a tree saying "I'm splitting in half." That's a removal, usually within days.
The included-bark V-union is a slow-motion structural crack. When two trunks grow up parallel with bark trapped between them, the union has no actual wood holding it together — just bark sandwiched between two trees. They look fine for decades and then one warm summer day with a heavy fruit or snow load, the whole thing splits and you have two half-trees crashing in opposite directions. We see this constantly with mature silver maples and Norway maples in Spokane.
How we decide: depth of crack, length of crack, location (trunk vs branch union), behavior (static vs dynamic), and target. A 4-foot vertical frost crack on the south side of a Ponderosa over an open lawn is monitor-only. A 2-foot dynamic crack across a co-dominant silver maple over your driveway is a removal call. The same crack 30 feet up on a healthy oak in the back forty is a wait-and-see.
Spokane / North Idaho Context
Spokane's freeze-thaw cycles produce more frost cracks than most regions. We have homeowners panic about long winter cracks every February that close back up by July. Resist the urge to seal or wrap them — the old advice to paint trunk wounds actually traps moisture and accelerates decay. Modern arboriculture leaves them alone.
What to do right now
- 1Measure the crack length and depth — photograph it monthly to track changes.
- 2Watch the crack during the next windstorm. If it visibly opens and closes, that's dynamic — call us.
- 3Never fill, seal, or wrap a trunk crack. Leave it open to dry.
- 4If the crack is at a branch union (V-split), reduce load by removing weight from one side — but only with professional help.
- 5Call (509) 204-4333 for a structural assessment.
What it costs: Crack assessments are free. Structural cabling to support a cracked union runs $300–$800. Removal of a tree with a failing crack typically runs $1,000–$4,500.
Frequently Asked Questions
Should I fill the crack with foam or concrete?
No. This is outdated advice that does nothing for structural strength and traps moisture, accelerating decay. Modern arboriculture never fills cavities or cracks.
Can a cracked tree be saved with cabling?
Sometimes. Dynamic cabling (flexible synthetic rope systems) can extend the safe life of trees with V-union cracks or codominant stems. Hardware cabling (steel rods through the wood) is older tech and creates entry points for decay. We use dynamic systems exclusively.
How fast can a cracked trunk fail?
It depends on whether the crack is static or dynamic. Static cracks can last decades. Dynamic cracks — opening and closing visibly during wind — typically fail within 1–2 storm seasons.
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