After a windstorm the explanation is always the wind. But two trees standing side by side in the same gust, one falls and one does not, and the difference is almost never the wind. It is what was already true about each tree.
Trees fail in three distinct ways, and each has its own warning signs.
Root failure, or windthrow
What it looks like: the entire tree tips over, lifting a plate of roots and soil. The trunk is usually intact. There is a crater where the root plate came up.
Why it happens here: this is the dominant failure mode in western Washington, and the reason is timing. Our damaging wind arrives between late October and February — precisely when the soil has been thoroughly saturated by weeks of rain.
Saturated soil loses shear strength. The root plate that held firmly in September loses its grip in December. The tree does not need extraordinary wind at that point; it needs ordinary wind against compromised anchorage.
This is why we see significant windthrow in storms that were not remarkable, and why the same trees stood through worse wind in summer.
What increases the risk:
- Root disease — laminated root rot in Douglas fir, Armillaria, and others reduce the anchoring system while the canopy still looks fine
- Severed roots from trenching, driveways, foundations, or grading, often years earlier
- Compacted soil from parking or equipment over the root zone
- Poor drainage, chronically wet sites, or a high water table limiting root depth
- Recent exposure — a tree that grew in a stand and lost its neighbors has not developed wind-firmness and is at elevated risk for several years
- Shallow-rooting species, western red cedar among them
Warning signs: soil cracked, mounded, or lifted on the side opposite a lean; new lean; a trunk that enters the ground like a pole with no flare; fungal fruiting at the root flare; a thinning canopy. Fresh soil disturbance at the base of a large tree is the most urgent sign on this entire page.
Trunk failure
What it looks like: the stem snaps, leaving a standing broken stub. The roots are intact and still in the ground.
Why it happens: almost always at a point already weakened. Sound wood is remarkably strong; it does not simply break. Look at the break and you generally find the reason — decayed wood, an old wound, a cavity, a crack, a previous topping cut, or a codominant union with included bark.
This is the failure that most surprises homeowners, because the canopy above the break was often full and green. A tree moves water through a thin layer under the bark, so it can look completely healthy while its interior structural wood has been consumed by decay.
Warning signs: conks or mushrooms on the trunk; cavities and old wounds; vertical cracks; a hollow sound when sounded with a mallet; visible sprout growth from old topping cuts; a V-shaped union with bark pinched inside.
Branch failure
What it looks like: individual limbs come down, tree remains standing.
Why it happens: deadwood, over-extended limbs with too much weight at the end, poor attachment, or included bark at the branch union. Wet snow and ice are as much a cause here as wind, since both add enormous weight to the canopy.
Least threatening to the tree, entirely capable of destroying a roof, a car, or worse. Most of the limb failures we respond to involved limbs that were already dead.
Warning signs: dead limbs held in the canopy; long horizontal limbs with heavy foliage at the tips; limbs over structures; previous limb failures on the same tree.
Why the same storm takes one tree and not the next
When a storm comes through Clark County and one tree in a row of five comes down, that tree had something the others did not. Usually one of:
- Root disease the others do not have
- Root damage from work done on that side of the property
- Recent exposure that left it carrying wind it never had to handle
- Internal decay in the trunk
- A structural defect at a union
- Canopy loaded heavily toward the direction of the wind
All six are findable before the storm. That is the entire argument for a fall inspection.
What to do with this
Match the intervention to the failure mode, because they need different things:
- Root failure risk — assessment, and often removal, because there is no way to rebuild an anchoring system. Reducing canopy can lower wind load on a marginal root plate.
- Trunk failure risk — assessment of remaining sound wood. Sometimes reduction lowers the load enough. Sometimes removal.
- Branch failure risk — the most fixable. Deadwood removal and end-weight reduction address most of it, at modest cost.
A hazard tree assessment identifies which mode a specific tree is vulnerable to, which is what makes the recommendation useful rather than generic. Where a defect is specific and the tree is worth keeping, cabling or bracing is sometimes the answer.
Cascade Tree Works serves Vancouver, Battle Ground, Camas, Brush Prairie, La Center, Washougal, Ridgefield, and Hockinson. Our ISA Certified Arborists can look at your tree and tell you plainly what it needs. Request a residential estimate.
