Jonna,
Try using some Round-up. Small amounts. I have heard that it caused some mutation in the new generation offspring. Some varigaited. Use on the ones you don't care about so if it kills it, no loss. This claim was disputed on my other garden web. One man said it works. Turns a $4 plant into a $80 plant but what if it wasn't stable. It's like buyer beware. But if you can and do experiment. Please keep us informed.
Stush
