Quinclorac and aminocyclopyrachlor leaching potential was evaluated in replicated field conditions in soil from five ecological sites of the Sheyenne National Grassland (SNG). Herbicide concentration was estimated using bioassays. Quinclorac did not leach past approximately 45 cm following 51 cm of precipitation applied over 9 wk and 15 cm of precipitation applied over 48 h. Aminocyclopyrachlor leaching was greater than quinclorac and moved through all soil types following both precipitation events. Quinclorac is suitable for use at the SNG to control leafy spurge; however, aminocyclopyrachlor will not be recommended. Control of yellow toadflax with aminocyclopyrachlor was evaluated at four growth stages. Control averaged 98% 1 YAT when aminocyclopyrachlor was applied before flowering but only 50% when the herbicide was applied to the fall vegetative stage. Yellow toadflax control with picloram plus dicamba plus diflufenzopyr averaged 92% 1 YAT and was not affected by growth stage.