Allow your boots to dry. Brush off dried grass pieces and other residue with a suede brush.
Combine 2 tablespoons of white vinegar and 2 tablespoons of warm water in a bowl. Moisten a cloth in the diluted vinegar solution. Blot the grass stains on your boots with the vinegar.
Press a dry cloth into the surface to remove grass stains.
Mix 1 tablespoon of dishwashing detergent with 2 cups of cool water in a bowl. Dampen a cloth with the diluted detergent solution. Dab the grass stain with the detergent mixture. Rinse your boots by sponging them with a damp cloth to remove the detergent solution.
Remove any remaining grass stains by blotting the stain with a solution made of 2 cups of cool water and 1 tablespoon of ammonia. Once the grass stains are completely gone, rinse the surface by sponging it with a damp cloth.
Wipe the boots with a dry cloth to remove as much moisture as possible. Place the boots away from heat sources and out of direct sunlight to air dry them completely.