Tide laundry detergent, alcohol and vinegar remove grass stains from clothes. Molasses and Karo syrup remove grass stains from clothes as well. Bleach with hydrogen peroxide is useful for removing grass stains from light-colored clothes.
Pour Tide laundry detergent directly onto the stain, and massage the stain. Let the detergent sit on the stain for 10 to 15 minutes, then wash the garment as normal.
Rubbing alcohol dislodges the green pigment from the grass. Dampen a sponge with rubbing alcohol, and wet the grass stain. Allow the garment to air dry, rinse it with cold water, rub laundry detergent into the stain and rinse again with cold water. Allow the wet area to air dry, then wash the garment.
Mix water with plain white vinegar, apply directly to the grass stain, then wash as normal. Avoid using fruit vinegar, such as apple cider vinegar, for this method. If the garment is light-colored, then mix 1/4 cup bleach, 1/4 cup peroxide and 3/4 cup cold water. Place this mixture directly on the stain, and massage into the stain. Allow the garment to sit for 30 minutes to 1 hour. Rinse thoroughly with cold water, then wash the clothing. Massage a few drops of molasses or Karo syrup directly onto the stain. Allow it to sit for a few minutes, then wash the garment to remove grass stains.
Clothing may require more than one treatment to remove grass stains. Pretreat and wash the item until the stains are removed, then dry according to the instructions on the garment's care label.