I just yank out a stem where ever I don't want one. It comes out, roots and all. Aggressive spreader, but easy to curb.

It may regrow from the root if you just cut it off at ground level. I find the stems break off at the soil level most of the time I try to yank it out--the root goes at 90 degrees to the stem. If you do this while the ground is soft, and try to wiggle it as you yank, you're more likely to get the root.