Herbs annual, 2–25(–30) cm. Stems 1–5 (sometimes appearing more numerous because of near-basal branching), branching throughout or in small plants often only above middle. Leaves: basal leaves withered or occasionally persistent at flowering; blade obovate to elliptic-oblong, 5–25 × 2–6 mm, apex usually acute to acuminate, occasionally obtuse; cauline blades elliptic-oblong (proximal) to lan­ceolate (distal), 5–15(–25) × 1–5(–12) mm, apex usually acute to acuminate, occasionally obtuse. Inflorescences dense to ± open, dichasial or occasionally distally mono­chasial cymes, usually not distinctly corymboid; pedicels 1–5(–11) mm. Flowers: calyx (3–)5–9(–11) mm; corolla (5–)10–15(–17) mm, lobes (1–)2–5 mm; anthers 0.7–1.1 mm; stigmas widely ovate to elliptic or orbiculate. Seeds dark brown or reddish brown. 2n = 36 (Europe, w Asia).

Phenology: Flowering spring (southward)–fall.
Habitat: Moist fields, other moist to wet, open places.
Elevation: 0–1500 m.

Distribution

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Introduced; N.B., N.S., Ont., Que., Colo., Conn., Ill., Ind., La., Maine, Md., Mass., Mich., Minn., Miss., Nebr., N.J., N.Y., Ohio, Pa., S.Dak., Tex., Vt., Va., Wash., Wis., Wyo., Eurasia, introduced also in West Indies, South America, Australia.

Discussion

There are historical records of Centaurium pulchellum from California, Delaware, and North Carolina.

In relatively large plants of Centaurium pulchellum in open habitats, the first branching is usually no more than three (rarely four) nodes above the base, with the branches being strongly divaricate. Each branch usually comprises a single internode, terminating in a central flower and two lateral branches, so that most of the plant above ground is a dichasial cyme. In C. tenuiflorum, the first branching is usually (four or) five or more nodes above the base, near or above mid-stem, with the branches diverging at narrower angles, forming a corymboid inflorescence more compact than that of C. pulchellum. In the flora area, however, C. pulchellum is usually represented by small plants that branch only above the middle. Such plants can be recognized as C. pulchellum by the consistently present although short pedicels and more slender stems, and sometimes by their occurrence with larger plants having the more usual branching pattern of that species.

Infraspecific taxa are sometimes recognized in Centaurium pulchellum in the broad sense in Asia. In the flora area, C. pulchellum is represented only by subsp. pulchellum.

Selected References

None.

Lower Taxa

None.