Herbs annual or biennial [perennial], chlorophyllous, glabrous [stems papillose-puberulent]. Leaves cauline, opposite, often also basal. Inflorescences dichasial or partly monochasial cymes. Flowers (4–)5-merous; calyx deeply lobed nearly to base; corolla pink to rose-violet or occasion­ally white [salmon, yellow], with whitish eye, salverform, glabrous, lobes abruptly spreading, elliptic-oblong, shorter than tube, margins entire or erose-tipped, plicae between lobes absent; stamens inserted in distal 1/2 of corolla tube, all initially deflexed to one side [not deflexed]; anthers free, coiling helically at dehiscence; ovary sessile; style deciduous, distinct, in most species initially deflexed away from stamens, shallowly cleft; stigmas 2, ovate, elliptic, or orbicu­late; nectaries absent. Capsules cylindric. x = 10; polyploidy frequent, aneuploidy occasional.

Distribution

Introduced; Eurasia, n Africa, Pacific Islands (New Zealand), Australia, introduced also in Mexico, West Indies, Central America, and South America, temperate to dry-mesic tropical regions.

Discussion

Species ca. 15 (3 in the flora).

Erythraea Borkhausen is a name formerly widely used but has been determined to be illegitimate.

G. Mansion (2004) and Mansion and L. Struwe (2004) concluded from molecular phylogenetic studies that the native North American species that had been included in Centaurium, with the exception of C. capense C. R. Broome in Baja California Sur, are more closely related to Eustoma, Sabatia, and the European genus Exaculum Caruel than to Centaurium in the narrow sense, and that Centaurium in the narrow sense is more closely related to the African genera Chironia Linnaeus and Orphium E. Meyer. They segregated the native North American species as Zeltnera.

The introduced Centaurium species often colonize disturbed sites, where populations may be of short duration. All of the species in the flora area are likely to be found in additional provinces and states and may disappear from others.

Plant size varies greatly within the species, being affected by environmental factors and by the interaction of photoperiod with the time of seed germination. The smallest plants often do not exhibit the characteristics of branching pattern, basal-leaf persistence, and flower size by which the respective species are usually distinguished.

Both outbreeding and autogamy probably occur in the species of Centaurium in the flora area. The style is at first deflexed in one direction and all stamens in the opposite. Later, both the style and the stamens become erect, at which stage autogamy may occur.

Selected References

None.

Lower Taxa

Centaurium erythraea, Centaurium pulchellum, Centaurium tenuiflorum

Key

1	Flowers with distinct pedicels 1–5(–11) mm, all plants with some pedicels 2+ mm.	Centaurium pulchellum
1	Flowers sessile or subsessile, pedicels to 2 mm.	> 2
2	Basal rosettes generally well developed and present at anthesis; corolla lobes (3–)4–8 mm.	Centaurium erythraea
2	Basal rosettes generally poorly developed or absent at anthesis; corolla lobes (1–)2–4.5 mm.	Centaurium tenuiflorum