Grass stains are one baby stain that can be a pill to get out, and while they're stubborn, they don't have to be permanent.
Make a paste out of an powdered enzyme detergent such as Wisk or Era. Then slather those grass stains with it and let them sit for no less than 30 minutes.
Then, grab an eyedropper and fill it with diluted ammonia or vinegar to bleach out any remaining color.
Finish it off with a regular wash cycle and those clothes should be good as new.

