Most gardeners invariably think of fertilizers as a good thing. But too much of a good thing can be deadly, and that goes for fertilizing trees. Providing a tree with too much fast-releasing fertilizer can burn the roots and lead to a quick death. In some cases this is what you want. A dead tree, whose roots are no longer strong and vibrant, can be much easier to remove from a landscape. If you have a tree you'd like to kill, this is one way to do the job.
Stop watering the tree you wish to kill. Allow the ground to dry out completely.
Spread at least three times the recommended amount of a high-nitrogen fast-release fertilizer around the intended tree. Fertilize out at least as far as the branches of the tree spread. Generally a tree requires 3 to 5 pounds of fertilizer per inch of trunk diameter measured 4 1/2 feet from the ground. Use at least 9 to 15 pounds of fast release nitrogen fertilizer per inch of trunk diameter to kill the tree.
Water the fertilizer into the dry soil around the tree. The majority of the tree's roots are within the first 12 inches of soil and almost half of the roots are within the top 4 inches of the ground for many species of trees so water the fertilizer into at least the top 4 inches of soil..
Spread at least three times the recommended amount of fast-release fertilizer around the tree a second time if the first application has not shown signs of working within 10 days. A second heavy application of fast-release fertilizer, watered thoroughly into the soil, should result in a quick death for the tree.