Centaurea (Knapweeds)

Flower Heads with Massive Spines
Caltrops Centaurea calcitrapa	Barnaby's Thistle Centaurea solstitialis
Flowers Bright Blue
Bachelor's Button Centaurea cyanus
Flowers Rose, Lavender, or Rarely White
Lower Leaves Heavily Subdivided
Spotted Knapweed Centaurea biebersteinii	Great Knapweed Centaurea scabiosa
Lower Leaves not Heavily Subdivided
Black Knapweed Centaurea nigra	Tyrol Knapweed Centaurea nigrescens	Brown Knapweed Centaurea jacea
	American Knapweed Centaurea americana