According to the search results, the tree is finally killed when its roots are uprooted and exposed to sunlight and air. The sun and air harden and wither the exposed roots of the tree and kill it. The tree goes through a process of browning, hardening, twisting, and withering before it ultimately dies. It is important to note that a tree takes a long time to die, and nature gifts every tree with a healing touch that wont allow it to die. If the tree is cut down, the bleeding bark will heal, and green twigs will appear from close to the ground. If left unchecked, the tree will expand again to its former size. Therefore, it is essential to ensure that the root is pulled out of the earth to kill a tree.