Centaurea nigra, commonly known as the black knapweed, is a herbaceous plant that belongs to the Asteraceae family. This plant is native to Europe and western Asia and has been widely naturalized in North America. It has a deep purple color and attractive flowers that bloom from June to September. There are several synonyms for Centaurea nigra, including the lesser knapweed, common knapweed, and hardhead. Although different terms are used to refer to this plant, the distinctive purple flower heads make it easy to identify. It is a popular plant for pollinators and is often used for decorative purposes in gardens and parks.