plants, it does not require any vectors for pollination. This allows for wind pollination over large distances, generating a large amount of genetic diversity. Another factor contributing to genetic diversity is the large amount of seed produced. Tall waterhemp in competition with soybean has been reported to produce from between 300,000 and 5,000,000 seeds per plant. Tall waterhemp also has a rapid growth rate, 50–70% greater than other annual weeds. Interspecific hybridization Interspecific hybrids of tall waterhemp and Amaranthus hybridus have been observed in experimental fields but have not been observed in agronomic fields. Agricultural impacts and control In North America, tall waterhemp is considered a major weed of agricultural fields and other disturbed habitats. The Southern Weed Science Society includes tall waterhemp on their list of weed species. However, it is not listed on the federal noxious weed list or any state lists in the United States. In Europe and other continents where the species has been introduced, naturalization is an infrequent occurrence. Because of the long germination window for tall waterhemp, a single herbicide application is unlikely to be an effective control strategy. Michigan State University Extension recommends a preemergence application followed by one or more postemergence applications. Some populations of tall waterhemp have been reported resistant to acetolactate synthase inhibiting (ALS) herbicides and the triazines, with some individual weeds being resistant to both herbicide groups. Resistance to acifluorfen and other diphenyl ether herbicides has been reported. Even more alarming is the emergence of waterhemp resistant to the latest generation of herbicides, HPPD inhibitors. Furthermore, waterhemp at a site in Nebraska was found to be resistant to 2,4-D, a phenoxy herbicide. According to Bob Hartzler of Iowa State University, the most effective control of tall waterhemp is achieved by cultural practices that promote growth of the desired vegetation. References External links Common Waterhemp // Mizzou WeedID Waterhemp, Common (Amaranthus Rudis L.) Waterhemp Take Action tuberculatus Flora of North America Plants described in 1849 Dioecious plants