Boiled water can also be used to kill weeds and prevent plant diseases around the garden. In fact, treating plants with hot water works effectively and sounds like one of the best and crazy home-made remedies. Gardeners generally boil water if they believe it contains chemicals or impurities that may be dangerous to the plant health. Theoretically, hot or boiling water kills most contaminants and makes the water safer for plants. But the boiled water must be cooled and bring to the room temperature before watering to plants.