Trees become overwatered when they are not allowed to dry out slightly between waterings. This happens because of wet climates, poorly draining soil, automatic watering systems and inexperienced gardeners. Root rot is the main problem with overwatering, signs of which include wilting or yellowing leaves. If the tree is planted in a soggy location, you may need to dig up the tree and relocate it. This is a last resort if nothing else works.
Stop watering the tree immediately and remove any sources of water if possible. Relocate your irrigation system or, if you have a permanent one on a timer, change the settings so it doesn't go off automatically.
Remove the top soil from around the base of the tree until you can feel the root system. Do this carefully and by hand as much as possible so you don't damage the roots.
Replace 1 inch of soil on top of the roots. This not only helps the root system breathe, but it also ensures that the tree trunk isn't buried too deep. Newly planted tree trunks that are too deep underground mimic the signs of overwatering, so this step ensures that the trunk and roots can breathe.
Apply 3 to 4 inches of an organic mulch, such as straw, around the tree. Make sure that the straw doesn't touch the base of the tree trunk. The mulch acts as a barrier and helps spread water so it drains evenly.