Herbicide-resistant giant ragweed and waterhemp continue to spread across the midwestern U.S. and are occurring more frequently in the same fields, making control with herbicides especially difficult. Weed biology is one of the most important factors to consider when developing a successful weed management program, with three main factors influencing success: 1) weed emergence patterns, 2) the weed seed bank, and 3) incorporating sound agronomic practices.