OK, I think we're straying a little bit off the point here!! LOL! Keep your mothers out of my mint, please!!

Thanks for the advice, though. I will do my best with Glyphosate and digging. An additional pain, though, is that the bed (and therefore mint) is against our neighbours fence, and I suspect the roots are reaching through to/from THEIR bed on the other side as well. So I may never be able to get rid of it completely...but I'll give it a go!!

Thanks!