Ortho GROUNDCLEAR® weed and grass killer2 works fast to kill weeds and grasses, with results you can start to see in 15 min. Apply any time of the year when weeds are small (3 in tall or wide) and actively growing. Mix Ortho Groundclear weed and grass killer with water (see label for instructions) and apply with a tank sprayer to weeds in patios and landscape beds and experience results quickly.