Salt kills vegetation and plant life. If you have a leyland cypress that has become too unmanageable or is blocking sunlight, salt is a natural and effective way to get rid of it. Using salt water, you will avoid using chemicals in your yard, but be careful about the method you choose for applying the salt. It can kill nearby plants if you're not careful. Although watering the ground around the trunk with salt water will kill the tree, it will also kill any surrounding grass and will stay in the ground for awhile, preventing anything new from growing.
Use a long drill bit to drill a ring of holes near the base of the tree at a 45 degree angle, facing downward.
Mix two parts water with one part salt.
Pour the salt water into the holes.
Plug the holes with mud. After a few weeks, the tree will be dead.
You can use sand instead of mud to plug up the holes if you desire. Gypsum can help soil heal from salting after the dead tree has been removed if there are any lingering issues.
Be sure you want the tree to die; you can;t reverse the process after pouring in the salt. Be careful not to let salt water slosh out as you carry the salt water to the tree.