Centaurea cyanus, commonly known as cornflower or bachelor's button, is an annual flowering plant in the family Asteraceae, native to Europe. In the past it often grew as a weed in cornfields (in the broad sense of "corn", referring to grains, such as wheat, barley, rye, or oats), hence its name. It is now endangered in its native habitat by agricultural intensification, particularly over-use of herbicides, destroying its habitat. It is also, however, through introduct (Wikipedia)

Centaurea calcitrapa is a species of flowering plant known by several common names, including red star-thistle and purple starthistle. It is native to Europe but is rarely found there, it is known across the globe as an introduced species and often a noxious weed. The species name calcitrapa comes from the word caltrop, a type of weapon covered in sharp spikes. (Wikipedia)

Centaurea pullata is a species of Centaurea found in Europe and North Africa.... (Wikipedia)