Common Centaury, European Centaury: Centaurium erythraea (Synonym: Centaurium umbellatum) - 5 petals.
Slender Centaury: Centaurium tenuiflorum - 5 petals.
Desert Centaury, Tall Centaury, Western Centaury, Great Basin Centaury: Zeltnera exaltata (Synonym: Centaurium exaltatum) - 4 petals.
Monterey Centaury, Muehlenberg's Centaury: Zeltnera muehlenbergii (Synonym: Centaurium muehlenbergii, Centaurium muehlenbergii var. albiflorum) - 5 Petals.