The present invention discloses that, propionic acid or salt thereof, is an effective pre-emergent and post-emergent herbicide. Propionic acid biodegrades first to acetic and formic acids and then to carbon dioxide and water thus posing not threat the environment. Propionic acid is less caustic and corrosive than formic acid, and with proper formulation and the use of respiratory protection, it poses no threat to the applicator. Propionic acid is demonstrated in this invention to control both monocotyledonous and dicotyledonous plants.