I planted horseradish iin the garden one year and dug it up in the fall And the roots were thin and long. Good flavor. Some of the roots snapped off way way down deep deep.
The next year it came back up 6 or 7 feet from where I planted it. I dug it up. And it snapped off way way down deep deep. Had good flavor. Long thin root.
The next year it came back up to 20 feet away from where it was planted. It is going to take a backhoe to dig deep enough to get all the root. If one little piece gets left in the ground, it will be back next year. Good luck.