How to Diagnose a Leaning Tree

Examine the tree closely for any signs of disease. Look for signs of decay, dead branches, rotten wood or open cavities on the tree that could be invaded by pests or disease.

Look for anything that may be pushing on the tree or weighing it down in one direction, causing it to lean. Another tree that's fallen onto it could cause it to lean. If part of the tree is caught beneath a fence, that could also cause it to lean.

Dig a little around the base of the tree. This is not to dig up the tree, but rather to examine the root structure and see if the tree's roots are growing over a rock, ledge or something else buried in the ground, such as a septic tank. Even if the tree is on even ground, the roots growing over something could cause it to lean.

Figure out if the tree was damaged in a storm. Trees that start leaning because of wind or other weather-related issues can become dangerous, particularly if another storm comes along.

Consult a professional arborist to see if he has an opinion as to why your tree is leaning. If it has been leaning for a long time, there may be clues he can read that are difficult for those who don't understand trees as well to see.