I think Sunflower is also used for lead removal ~~~~~~~~~~~~~~~~~~~~~~~~~~ have an article in this months local growing mag about sunflowers, which I think you may find interesting.... "Studies have found that sunflowers act like natural vacuum cleaners when it comes to cleaning up contaminated soils and polluted groundwater.By a process known as phytoremediation, the plants suck contaminants out of the soil and store them in their stem tissue for easy disposal. In the early 1990's, a New Jersey company planted sunflowers around a badly polluted pond near the Chernobyl nuclear plant.The plants removed 95 per cent of the radioactive strontium in the soil"