The short answer
Work neat white vinegar or surgical spirit into the mark before it ever sees water, leave it ten minutes, then wash.
- Do not rinse it first. Water on a grass stain sets the chlorophyll into the fibre.
- Work in white vinegar or surgical spirit with an old toothbrush, following the weave rather than scrubbing in circles.
- Leave it ten to fifteen minutes.
- Wash at the highest temperature the label allows. For white cotton, oxygen bleach in the wash will lift what is left.
What will ruin it
Chlorine bleach on trainers with any coloured trim or glue line will yellow the white and eat the adhesive. Oxygen bleach, the powdered kind sold for laundry, is the one for this job.
Why it works
Chlorophyll is a dye, not a dirt, and it bonds with plant proteins on contact with water. Getting a solvent in before water does is the whole trick.
Household chemicals can be dangerous in combination. Never mix them, keep the room ventilated, and test anything on a hidden patch first. Full disclaimer.
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