I'm interested in the idea of a duckweed pond. Is there enough known about these to be sure I wouldn't be creating some sort of nasty mutant plant that would end up choking out other plants in my yard, or in the neighborhood? (A genuine question, I'm not at all familiar with this plant.) And assuming it's benign, how is it used as a source of human food? Is it a vegetable that one cooks, or a salad green, or something quite different again?