One safe way to kill weeds without harming other plants is to remove the weeds by hand. Chemical herbicides can be used as long as the treatment is applied only to the weeds.
To kill weeds by hand, carefully dig out the entire plant. Make sure the whole root system is removed to prevent re-growth. Apply corn gluten to the soil as a pre-emergent treatment to prevent new weeds from growing. To keep chemical herbicides from harming plants, do not spray weeds on windy days. Another way to protect other plants from overspray is to cover them with light plastic sheeting before treating the weeds.