Signs a Tree Is Dead or Dangerous: When Removal Is the Safe Call

Most trees that come down on a house or a car did not fail without warning. They leaned a little more each season, lost crown from the top down, pushed mushrooms out of the trunk, or lifted the soil at their base. The signs are readable from the ground if you know where to look. This guide walks through the main ones and sets out the honest dividing line: the trees that can be watched or pruned, and the trees where removal is the responsible call.

Start with the crown

Walk far enough back to see the whole crown, then compare it with the same species nearby. A healthy crown is full and even. A tree in decline loses the top and the branch tips first. Arborists call it dieback, and the share of the crown that is dead is one of the first things we note on an assessment. A tree with a small amount of deadwood at the tips may be stressed and still recoverable. A tree with a third or more of its crown dead is telling you the decline is well advanced, and a tree that leafs out on only a few low limbs is close to gone. Two cautions. First, judge deciduous trees in leaf, not in January: a bare valley oak in winter is dormant, not dead. Second, watch the trend, not the snapshot. A crown that thins further every year is a different case from a thin crown that holds steady.

A lean that is new, or getting worse

Plenty of sound trees lean. A tree that grew toward the light for forty years and carries a full, healthy crown is usually fine standing exactly as it is. The lean that matters is the one that changed. Watch for a lean that appeared or increased in the last few years, soil lifting or cracking on the side opposite the lean, and roots pulling out of the ground on the side the tree leans away from. That lifting is called root plate movement, and it means the roots that anchor the tree are letting go. A tree can stand for years on a weak root plate and then go over in one night of wind and wet soil. If you are not sure whether a lean is new, old photos help. Fresh cracks in the soil at the base are a reason to keep people and cars out from under the tree and get it assessed promptly.

What the trunk is telling you

Get close to the trunk and read it from the ground up.

• Fungal conks and mushrooms. Shelf-like fungi growing from the trunk or from the roots at the base are not growing on the tree. They are growing in it. Conks are the fruit of decay fungi that digest wood inside the trunk, and by the time they show on the surface, the decay inside is usually well established.
• Bark sloughing off. Bark that peels away in patches and does not grow back means the wood under it is dead. Large areas of missing bark, especially around most of the trunk, point to a tree that is dead or close to it.
• Cracks and seams. A deep crack running up the trunk, or a seam where two sides of the trunk are separating, is a structural defect. So is a trunk that has split at a union and started to open.
• Weak unions. Two trunks or large limbs that meet in a tight V, with bark trapped inside the join, form a weak union. These unions split apart under load, because the trapped bark means the two sides were never properly joined.
• Hollow sounds. Knock on the trunk with a mallet or the handle of a tool. A solid trunk answers with a dense thock. A hollow trunk sounds like a drum. A hollow sound alone does not condemn a tree, since many old trees stand safely with hollow centers. Combined with cracks, conks or a big dead crown, though, it adds up to a removal conversation.

Check the ground at the base

The roots hold the tree up, and their condition shows at the surface. Look for soil heaving on one side of the trunk, mushrooms growing in a ring or cluster at the base, and a trunk base that flares oddly or not at all. A healthy trunk widens where it meets the ground. A trunk that goes straight into the soil like a post can have buried or damaged roots. Roots cut by a trench, driveway or footing can kill a tree slowly, with crown symptoms arriving two or three seasons after the digging. If your tree started dying back after work near it, that history is worth telling whoever assesses it.

San Gabriel Valley species notes

Local species fail in local ways, and two patterns come up again and again in our foothill neighborhoods.

Eucalyptus. Tall eucalyptus across Altadena and Pasadena carry heavy limbs on wood that can let go with little warning. Arborists call it limb drop: a large, apparently healthy limb breaks and falls, most often in calm, hot weather. A eucalyptus with dead limbs in the crown, cracks at the limb unions or a history of dropping wood should be assessed, and its crown kept pruned back from roofs and parking areas.

Pines. Pines attacked by bark beetles die fast. The signs are a crown that fades from green to yellow to rust red across the whole tree, small holes in the bark, and pitch tubes or boring dust at the base. Once a pine's crown has turned, the tree is dead, and dead pines get brittle quickly. A dead pine near a house should not sit on a someday list.

Whatever the species, rapid change is the through-line. A tree that was full last spring and thin this spring is asking for attention now.

Assessment, pruning, or removal: how the call gets made

The deciding question is not only whether the tree is failing. It is what the tree can hit. Arborists call whatever sits within reach of a falling tree or limb its target: a roof, a bedroom, a sidewalk, a parked car, a play area. A declining tree in the back corner of a big lot, with nothing under it, can often be pruned, reduced and monitored. The same tree over a roof usually cannot.

Pruning fixes some problems. Deadwood removal takes brittle wood out of the crown, and a careful reduction can lower the load on a weak union. Our tree trimming and pruning page explains how that work is scoped. Pruning does not fix root plate failure, deep trunk cracks, or decay that has hollowed most of the trunk. When the structure itself is going, removal is the safe call, and it is calmer and cheaper done on a schedule than after the tree picks its own timing.

Permits still apply. A dead or dangerous tree can still be a protected tree, and several valley cities protect oaks and other species whether they are healthy or not. Before any removal we check the rules for your address, the same check described in our guide to protected trees and permits. Homeowners in Altadena and Pasadena can read the local picture on our city pages.

If a tree on your property is showing two or more of these signs, get it looked at. The assessment is free, and the answer may be simpler than you fear. If the answer is removal, our tree removal page explains how we scope and rig the work.

General guidance only. Tree condition and risk can only be judged in person, and a tree that looks sound from the ground can still hide defects. If a tree is leaning over a house, lifting at the base, or dropping limbs, keep people away from the area under it and have it assessed.