Tropical Aster, Ironweed, Bitterleaf. Vernonia is known for having intense purple flowers. The genus is named for the English botanist William Vernon. Common names include bitterleaf, ewuro, ndole and onugbu. They are common in most West African and Central African countries. They are one of the most widely consumed leaf vegetables of Cameroon, where they are a key ingredient of Ndolé. The leaves have a sweet and bitter taste. They are sold fresh or dried, and are a typical ingredient in egusi soup.