Posted: 01/11/2015 at 22:47
The only really effective treatment is to spray with glyphosate when it is growing strongly and then wait for it to die back completely which ensures the roots are killed too. A few new growths might reappear which you would again treat in the same way.
However, if you don't want to use any chemicals at all then there is a solution: Dig as much out as you can and then pull up every new growth you see immediately. It may take years but you will eventually beat it that way as no plant can survive without leaves to feed the roots.