Stain removal is all about speed and technique. Here's the proven method for tackling grass stains effectively.
Apply Power Wash Laundry Detergent directly to the grass stain. Work it in with an old toothbrush using small circular motions.
Soak the stained area in white vinegar for 30 minutes. Vinegar breaks down the chlorophyll and plant proteins.
Make a paste of baking soda and a few drops of vinegar. Apply to the stain and scrub gently. Let sit for 15 minutes.
Wash on the warmest setting safe for the fabric. Check the stain before drying -- heat sets grass stains.