So, I've been battling thistles ever since we had a crazy next door neighbor several years ago that would only mow his yard 2 or 3 times per season. I've tried both Roundup 365 and Ortho Ground Clear Year Long and as far as I can tell, they barely hurt their feelings, let alone kill them. Is there something else that is effective on thistles? I know we can't get dioxin (Agent Orange) anymore but I'd like something that potent.