Wisconsin is home to 13 species of Pigweeds (plants in the genus Amaranthus). Of these species, two (red-root pigweed and smooth pigweed) are widespread in Wisconsin and have historically plagued farmers as competitive weed species. With the rapid increase in herbicide resistance, concern exists with respect to the spread of two particular pigweeds that have historically been called uncommon: common/tall waterhemp (Amaranthus tuberculatus) and Palmer amaranth (Amaranthus palmeri). These species are of higher priority to prevent spread compared to other pigweeds as they have been found to develop resistance to multiple herbicides and be more competitive.
Soil Science Extension
University of Wisconsin Madison