[Wikipedia] Native Range, Medicinal Properties, Edible Weed: It is native to North America and parts of South America. In Brazil it is known as acariçoba and has applications in herbal medicine with purported anxiolytic, analgesic and anti-inflammatory properties.[2] It can also be found growing as an introduced species and sometimes a noxious weed on other continents. It is an edible weed that can be used in salads or as a pot herb. (link added by Mary Ann Machi)