Posted: 11/03/2012 at 22:36
I heard Bob flowerdew talking about this on a GQT one Sunday and he said he uses a blowtorch on his. I know this sounds drastic but he said it does something to the plant and kills the roots as well. I think he said you have to wait until there are good sized leaves to zap. Sorry I can't remember the exact details but I am going to try it this year when the shoots start appearing.
Hope this helps and do take care!