My husband lined a long flower bed with Big Blue Liriope. It started getting out of control rapidly and that is when I learned how aggressive it was and that it is Roundup resistant. The only way I can get rid of it is to dig it up. I'm in zone 5 / 6. So, when weeds get into it, I spray it with RoundUp. The weeds die but not the Liriope. You would need to make sure the variety you have is resident via a small test. I know people hate using chemicals, but sometimes it is the only reasonable solution.