Buy any herbicidal product that contains glyphosate for effectively killing an unwanted tree, as recommended by the Washington State University Extension. Select an undiluted, water-soluble formula, as this has higher efficacy than the esters or oil-soluble formulas.
Cut down the tree to a 2- to 3-foot-tall stump, using a sharp ax. Make sure the stump surface is level and smooth to keep the herbicide from flowing off.
Spray the herbicide on the entire surface of the stump if the stump diameter is 3 inches or less. If the stump diameter is larger, spray only the 2 to 3 inches next to the bark, as the heartwood of larger trees is already dead.
Repeat treatment after seven to 10 days. Avoid the use of glyphosate on very hot days or on trees that are severely stressed by drought. Although you can use the chemical at any time of year, the recommended time is August or September.
Leave the dead stump as it is or use a stump grinder to grind it to about a foot below the soil line. This is the recommended method of stump removal in urban settings, cites the University of Minnesota Extension.