Character

Centaurea
calcitrapa

Centaurea
melitensis

Centaurea solstitialis
epappous form

Centaurea solstitialis
pappous form

fruit appearance

pericarp with brown mottling,
dull to shiny,
glabrous

pericarp grayish to purplish-brown,
shiny,
pubescent

pericarp with brown mottling,
dull,
glabrous

pericarp light brown with some darker mottling,
shiny,
glabrous

pappus color

pappus absent

tan

pappus absent

white

fruit attachment scar notch shape

mildly hooked

very strongly hooked

mildly hooked

strongly hooked

fruit width

1.5–2 mm

1–1.4 mm

0.9–1.2 mm

0.9–1.2 mm