I have a bed full of the darn stuff. Roundup does very little to help. I go through and pull when I have time. Any other tips? This stuff has been there for years, and will probably outlive me!
recommend applying roundup with a brush, then reapplying and again and again. Never let the plants get very large, or they get more energy to send out more underground runners. Is it around other plants or isolated by itself? If around other plants you have a challenge! Eventually it will give up, but it takes a lot of persistence.