Figure. Compare and contrast reproductive structures produced by different pigweed species. Image courtesy of University of Illinois Extension. While not everyone in northwest Minnesota has had the 'joy' of trying to manage waterhemp in broad leaved crop fields just yet, those that have can attest to the difficulty of trying to stay on top of a weed that can emerge long after both pre- and post-emergence herbicides have broken down. Palmer amaranth is in the same family of weeds as waterhemp but as it is not native to Minnesota, has the capacity to produce large quantities of seed and a fast rate of growth is considered a noxious and invasive weed that is prohibited in Minnesota and must be eradicated.