Aminopyralid is in the pyridine carboxylic acid family with a synthetic auxin mode of action leading to abnormal growth, particularly at the apical points, and eventual death. It is a broadleaf-selective herbicide with no known efficacy on grasses but is highly effective on legume and aster species. Unlike TCP, AMP can exhibit residual soil activity resulting in root uptake by neighboring plants, and the suppression of seed bank germination.