The sooner you treat it, the better! That goes for all spots, but especially for grass stains. Give the grass stain no chance to secure themselves! There are two good treatments for grass stain with little risk. Make the following recipe: 1 part ammonia, two parts pure alcohol and three parts hot water. It is important that the mixture is warm, otherwise it does not work. When the mixture cools down heat it up again. With this mixture and some clean cotton we tackle the grass stain. If the stain is still new, we might get rid of it with hot soapy water. If that does not work, we treat the stain with alcohol and even if that does not help us, we give it a treatment with ammonia (about 5%).