Horseradish! Put it a really good sized pot and let it grow! "They" always say mint grows like crazy but I never felt like it was really out of control by any means, horseradish either but as a precaution i stuck some in a pot some time ago to test it out. In our high desert climate I welcome plants that grow happily. We dug it up and scrubbed it and threw it in some vodka with whole black peppercorns(more on that later).