Answer: Horseradish is tenacious, there's no doubt about it. Unfortunately, like dandelions, the roots grow extrememly deep and are survivors. Repeated chopping or mowing in spring will eventually deplete the roots' reserves and kill the plant. Or you can cover the area with landscape fabric and plant preferred flora through it.
Another option is to give away the crowns of rhubarb and horseradish roots in a "dig your own" day -- invite neighbors to take them away for the digging. And I know you'll be sure to give them fair warning about the abundance to follow. Best of luck!
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