[header] How to kill a tree [title] Remove any loose bark. [step] Girdling is a method for killing a tree by interrupting the flow of sap between the roots and crown of the tree. You can girdle a tree with or without the use of herbicides to speed the process along. 
Girdling is the easiest and most popular method for killing a tree without chemicals when no herbicides are used, but the tree will take many months to die from the process. Start by pulling away any loose bark that gives you easier access to the trunk.