Wow. Thanks Nino and doom. Good information. Course I'm not sure what to do now. Maybe I'll put a couple of smaller ones in pots and think about it. Try to kill the others and see if I can use the roots. Sorry to do it, but 6 foot plants with burrs is not a fun idea for my back yard.
Thanks again for your research. glo
p.s. if someone wants it and to come dig it up, mi casa es su casa. :=]