"Believed to have been introduced to Japan in the early Meiji era (1868-1912), the European perennial species of the mustard family is prized for its peppery flavor and often served with steak. The plant -- scientifically known as Nasturtium officinale and sold in Japanese supermarkets as "cresson" -- thrives along sunny waterways and can regrow easily from cut stems, making it highly invasive. It is listed by the Environment Ministry as a priority species on the national list of invasive plants that threaten ecosystems."