centaurea nigra

Centaurea nigra is a species of flowering plant in the daisy family known by the common names lesser knapweed, common knapweed and black knapweed. A local vernacular name is hardheads.

It is native to Europe but it is known on other continents as an introduced species and often a noxious weed.

Although the plant is often unwanted by landowners because it is considered a weed by many, it provides a great deal of nectar for pollinators. It was rated in the top 5 for most nectar production (nectar per ...