I know! If only they ate ivy....
I believe the weedwhacker will work, if you use it frequently enough and basically keep a bare trench around the edge. You may have to occasionally pull some eager scouts -- probably will! but my experience with ivy is that if you catch the new growth when it's young it's pretty easy to yank it right outa there.
Good luck! Er, also probably you'll want to watch out for it colonizing your containers up through their drainage holes.... so, trays underneath?
