Leaning trees: when a lean is normal and when we tell people to take it down

By Kendrick Hunter, owner of Hunter Excavating in Durham, NC.

Short version: the lean is almost never the problem. What matters is whether the tree grew that way or moved that way. A tree that has leaned since 1987 has spent forty years building wood to handle it. A tree that leaned last Tuesday is falling down slowly.

The way you tell them apart is the shape of the trunk and the condition of the dirt at the base. Two things, both free to look at, and most people have never been told to look at either one.

I get called out to leaning trees constantly around Durham. Probably a third of those calls end with me telling somebody their tree is fine and they do not need to pay me anything. I would rather do that than take money to remove a healthy oak because it looks crooked.

Why most leaning trees are fine

Trees lean toward light. That is the whole explanation for the majority of what I look at. A tree at the edge of a wood line, or squeezed between a house and a garage, or growing on the north side of something tall, will grow out toward the opening. That is not a defect. That is a tree doing exactly what it evolved to do.

Trees on slopes lean too, and Durham has plenty of slope, especially the properties dropping toward Ellerbe Creek or down through the Eno watershed. Same idea.

What makes those trees safe is that they built for it as they grew. A tree responds to a sustained lean by laying down extra wood to compensate. Hardwoods do it on the upper side, in tension. Pines do it on the underside, in compression. Either way the tree has been quietly reinforcing that lean for its whole life, and the root system on the tension side has thickened to match.

You cannot get that from a tree that tipped over in a storm three weeks ago. It has not had time.

The first thing I look at: is the trunk curved or straight?

This is the tell, and it is simple enough that you can do it from your driveway.

Find where the trunk comes out of the ground and follow it up with your eye. If the base curves and the tree gradually straightens as it rises, so the whole thing has a sweep or a soft J shape to it, that is an old lean. The tree leaned, then grew back toward vertical over years. That shape takes decades to build and it is evidence that the tree has been managing this the entire time.

If the trunk is dead straight and the whole tree is tilted, like a fence post somebody shoved, that is a new lean. The tree grew up vertical and then something moved it. Ninety percent of the time that something is the roots.

Straight trunk plus a lean is the shape I do not like.

The second thing: what the ground is doing

Walk to the base and look at the soil on the side opposite the lean. That is the tension side, where the roots are being pulled up.

What you do not want to see is a crack in the soil, a mound or heave where the ground has lifted, roots showing that were not showing before, or a gap opening between the trunk and the dirt. In Durham's red clay this often shows up as a clean crescent shaped crack a few feet out from the trunk, sometimes with the turf pulled apart along it. Clay cracks in a way that sandy soil does not, which is one of the few times our soil does us a favor. It tells on the tree.

ISA's consumer brochure on recognizing tree risk (PDF) lists this under root failure and makes the same point I am making: soil cracking or separation matters most when the tree is leaning. The two findings together are much worse than either one alone.

Also look for a proper root flare. The trunk should widen where it enters the ground, like a foot. If the tree goes into the soil like a telephone pole with no flare, either it was planted too deep or the flare has rotted, and neither is good news under a leaning tree.

Mushrooms or shelf fungus at the base means decay in the root collar. A leaning tree with conks at the base is not a maybe.

How to tell whether it is still moving

If you are not sure, measure it and wait.

Drive a stake in the ground a set distance from the trunk and photograph the tree against it, same spot, same angle. Or pick a fixed reference already there, a corner of the house or a fence post, and take the photo from a marked spot on the driveway. Repeat after the next few hard rains.

A lean that is not changing is usually a lean you can live with. A lean that visibly increases after a storm is a tree that is failing in slow motion, and slow motion still ends the same way.

Worth saying: this only works if there is time. If the tree is over a bedroom and it moved last night, do not start a monitoring program. Call somebody.

When we tell people to take it down

I am not squeamish about removing trees, and I am also not going to invent a reason. Here is what actually gets a removal recommendation from me.

A straight trunk with a fresh lean and soil heaving or cracking on the tension side. That is active root failure and it does not reverse.

A lean that has measurably increased, especially after a wet spell. Once the root plate starts moving, the leverage gets worse every time it moves.

Any lean over an occupied structure combined with decay at the base or in the root collar. The lean tells you the direction and the decay tells you the timeline.

A hollow trunk with a lean. Hollowness alone is survivable for a lot of trees, since strength lives in the outer wood. Add a lean and you have loaded a tube from the side.

Loblolly pines in a saturated yard, leaning toward the house. I wrote about the soil part of this in our post on hurricane season tree prep, but the summary is that our clay loses its holding strength when it is soaked, and a shallow-rooted 90-foot pine that is already tipped does not need much wind after that.

When we tell people to leave it alone

An old sweeping lean with no soil disturbance, a sound flare, and no decay. Leave it.

A lean that points away from everything you care about. Risk is a combination of the tree failing and something being there when it does. A tree that would drop into the back corner of a wooded lot is a different conversation from the same tree over a driveway.

A small tree. Fixing a lean on a young tree with staking is reasonable. Trying it on a mature one is not.

Three things people try that do not work

Cabling a mature leaning tree to a stake or a deadman in the ground. The forces involved are enormous. That hardware is holding nothing. Cabling between two stems inside a tree is a real technique with real specifications, and it is a different thing entirely from tethering a tree to the yard.

Cutting the top off to lighten it. This is topping, it does not fix a root problem, and it produces weakly attached regrowth that makes the tree worse over the following years. More on why we refuse to do that in the hurricane prep post.

Pruning everything off the leaning side. You have not moved the center of gravity much, you have wounded the tree, and the roots are still coming out of the ground.

The Durham situation nobody connects

Here is one I see often enough that it is worth its own paragraph. Somebody does work in the yard, a new driveway, a trench for a line, a retaining wall, some regrading, and cuts roots on one side of a big tree. Nothing happens. The tree looks fine that year and the year after.

Then, three or four years later, it starts leaning away from where the roots were cut.

Because we do excavation and grading as well as tree work, I end up on both sides of this. If you are planning work near a mature tree, the root zone extends much farther than the branches do, and the structural roots are shallower than most people picture. It is a lot cheaper to route around them than to remove the tree later.

Questions we get about leaning trees

My tree started leaning after a storm. How urgent is this?

Urgent if the trunk is straight and the soil at the base is cracked or mounded. That is root failure in progress and it can finish in the next storm. Keep people out of the fall zone and get somebody to look at it soon.

The tree has leaned for as long as I have owned the house. Should I worry?

Probably not, if the trunk curves, the base is sound, and the ground is undisturbed. A long-standing lean with a curved trunk is usually a tree that solved this problem before you moved in.

Can you straighten a leaning tree?

On a young tree, sometimes, with proper staking for a limited period. On a mature tree, no. Anyone offering to winch a big tree upright and stake it is selling you something that will not hold.

Does homeowners insurance cover removing a leaning tree before it falls?

Generally no. Most policies pay for removal after a tree damages a covered structure, not for preventive removal of a hazardous one. That is frustrating and it is worth confirming with your own agent, because terms vary and I am a tree guy rather than your adjuster.

Do I need a permit to remove it in Durham?

On residential property, almost never. Details are in our post on Durham tree removal permits.

If you have one you are unsure about

Send a photo or have us come look. We do free on-site quotes, and a fair number of those visits end with me telling you the tree is fine.

Hunter Excavating 1904 Front St Suite 410, Durham, NC 27705 (336) 988-7585 Hunterexcavatingllc@gmail.com Mon to Fri 8:00 to 5:00, Sat 8:00 to 1:00

Veteran-owned and based in Durham, working across the Triangle including Raleigh, Cary, Chapel Hill, Hillsborough, and Mebane. More on our tree removal services in Durham, NC, including trimming, pruning, stump grinding, and lot clearing.