Using veggy cooking water for your plants.
I read that water from boiling potatoes was good for spraying whitefly. I then read it was also good for watering your plants as the starch spurs the release of plant nutrients in the soil. In fact most veggy cooking water is good for your plants including pasta water and water from boiling eggs which contains calcium. However added salt is not good for them but I don't add salt to potatoes anyway. I do save some veggy water for stock and gravy but will definitely use any surplus for my plants.