Question
I have an elderly customer with failing eyesight is tripping over several roots from three mature cottonwoods in her yard. Would grinding the roots down to ground level kill the tree or cause it to fall over in a storm.  

Answer
William, Grinding the roots down to the ground would definately NOT be healthy for the tree. This will make the tree unstable, and open wounds that are attractive to insects and disease. I advise against it. Good luck!

          Regards, Gary Overton