Seven Signs a Tree Is About to Fail

Most people call a tree service because of a feeling. The tree looks wrong, or it made a noise in the last storm, and now they cannot stop looking at it.

Sometimes the feeling is right. Here is what a certified arborist checks, ordered roughly by how much it should worry you.

1. The ground is heaving on one side

Look at the soil around the base, especially on the side opposite any lean. Cracked, raised, or mounded soil means the root plate is lifting. That is the tree beginning to tip.

This is the most urgent sign on the list. A root plate that has started to move does not stop, and the failure when it comes is the whole tree rather than a limb.

2. A vertical crack running up the trunk

A seam running up and down the trunk, particularly one that opens and closes as the tree moves in wind, means the trunk is separating. Get it looked at now.

Horizontal cracks and bark fissures are usually normal. Vertical seams are not.

3. A sudden lean

Most trees lean. A tree that has always leaned the same amount is generally fine, because it has grown reaction wood to compensate.

A lean that appeared recently, or one that has increased since last year, is a different situation. If you have an old photo of the tree, compare it.

4. Mushrooms or conks at the base

Fungal fruiting bodies at the root flare or on the lower trunk mean decay inside the tree, and by the time mushrooms appear the decay is usually extensive. The tree can look completely healthy above and be structurally hollow at the base.

This one fools people constantly, because the canopy gives no warning.

5. Co-dominant stems with included bark

Where a trunk splits into two roughly equal stems, look at the union. A U-shaped join is strong. A tight V, especially one with bark growing down into the seam, is weak, because the bark prevents the two stems from actually growing together.

This is the classic failure point on Bradford pear and silver maple, and it is what takes those trees apart in a straight-line wind. It is also the one defect that hardware can sometimes fix, with a cable installed high in the canopy.

6. Dead limbs in a live canopy

Look up in mid summer when everything is leafed out. Bare limbs against a full canopy are dead, and dead limbs come down on their own schedule.

This is a maintenance issue rather than an emergency, unless the dead limbs are over a driveway, a patio, or anywhere people sit.

7. Thinning that starts at the top

A canopy that is dying from the top down usually means a vascular problem, meaning the tree cannot move water. In northeast Kansas the most common cause on ash is emerald ash borer. On other species it can be root damage, construction impact, or drought stress.

What matters as much as the defect

Arborists assess risk as a combination of two things: how likely the tree is to fail, and what it would hit.

A hollow cottonwood in the back corner of ten acres is a low risk tree. The same tree over a driveway where cars park is a high risk tree. The defect is identical. The consequence is not.

So when you are deciding whether to spend money on a tree, ask both questions: how likely is it to fail, and what is underneath it.

When to get it assessed

Signs one, two, three, and four are worth a call this week. Five, six, and seven are worth a call this season.

A written risk assessment costs a fraction of a removal and frequently ends in something other than a removal. If you are an HOA or a property manager, the written record matters for a second reason, because it is what your insurer will ask for if a limb ever comes down on someone.