Articles

What to Do About Leaning Trees

Leaning trees should be inspected to determine risk to nearby people or property and any potential corrective actions.

Save for later Print

Updated:

April 12, 2023

Skip to the end of the images gallery

This crabapple tree stands long after the roots and soil gave way in the past. Photo: Scott Sjolander, Penn State Extension.

Skip to the beginning of the images gallery

During windy weather, trees may be blown into leaning positions and remain there after the event. Can one bring it back upright and expect it to stay? This question often comes after storms occur and recent landscape installations are shifted.

A tree lean might be defined as occurring when the main stem deviates from vertical. Tree leans can include three types: bows, straight leans, and sweeps. It might be vertical at the ground and start an arc toward horizontal, known as a bow. Bows often result from the weight of snow or ice on the stem. A straight lean starts right from the ground, with the stem remaining straight, but bent at an angle from the usual vertical. These straight leans typically occur as the result of a discreet event, throwing off the structural stability of the tree. Sweeps are leans where the tree self-corrects the lean, often noticeable years after a lean occurred in the first place. Sweeps may also result from trees growing towards sunlight. A sweep starts from a lean at the ground and curves upward. Sweeps form slowly as the tree adds wood to support the lean year after year, meaning sweeps are often structurally sound.

Because of the potential risk they create, here we focus on straight leans, more commonly referred to simply as leans. After a lean occurs, one might consider righting the planting if a small tree or bush is simply tipped and loose in the planting space. On the other hand, a large tree with a heavy root ball and torn roots is probably not practical to bring back to an upright position and anchor. Knowing how large a plant to venture an effort on can save frustration, expense, and injury.

A young tree in a straight lean at a park — This small tree was planted in the prior fall, and it was blown into a lean in a spring windstorm. Photo: Hannah Bequeath, used with permission.

Small plants, such as the ten-foot-tall tree in the photo above, might be righted successfully if the trunk is not broken, and the stressful condition is not likely to repeat. An example of such an event might be if a car or animal accidentally knocked the tree. On the other hand, if a deer was repeatedly marking territory by rubbing the tree, the effort might require a couple more steps. The tree may need anchoring by one, two, or three lines and stakes. Further, sturdy fencing or barricades might be needed to keep the offender away until the tree grows large enough to discourage repeated breakage.

Trees gain strength by adding wood to counteract forces that may push, pull, or twist their structure. When the tree's structure is strong enough not to be broken by the force, the stress stimulates a growth response. If the tree has enough resource reserves to recover, it survives and grows into its new environment, with the lean developing into a sweep. Healthy trees do this all the time, and we see sturdy, well-buttressed trees as evidence. Trees that are too weak or too broken to recover may survive in an altered position, or they may break. Others may survive with defects that may cause the tree to fail later.

Ideally, any anchoring or bracing should allow the tree to move and build system strength. Wherever the assistance is applied, it creates a new structural stress where the tree is more likely to break until it compensates by adding sufficient wood to counter the new forces and movement it experiences. Any wounding or defect in the system stays where it is, and the tree grows around it. Trees do not heal wounds like people do. Wounded material is not repaired; it is isolated and covered over.

What to do about the small tree in the photo above? This tree stands on a very storm-prone site. I suggested a remedy after checking that if the roots were sound, and that the tree was not broken. My suggestion was to anchor the tree with one or two stakes and lines in the direction that most windstorms come from. Set the lines without tension, so that the tree can move and grow in compensating strength, but not to be blown over in normal storms. One must judge what a normal storm is at that site, and reading the landscape will help in deciding.

However, do not limit the inspection to that of the tree above ground, but look further at the roots and the soil around the tree. If roots are broken or the soil itself fails to hold a root system intact, the soil may be heaved up on the back side of the lean. Trees may be uprooted or fall in wet soils and lift the root plate on the back side. It will be difficult to re-anchor the tree successfully if either root or soil failure happens. On the other hand, some trees may stand this way long after the event. If keeping a tree in this condition, limit your risk by removing people or objects or things that may be harmed if the tree falls.

Further, some leaning trees may become unsafe right away, or in the future. Be sure to obtain the services of professionals able to do this work. It's dangerous to owners, passers-by, and to innocent victims unable to see the situation.