Centaurea solstitialis

Linnaeus

Sp. Pl. 2: 917. 1753

Common names: Yellow or Barnaby star-thistle St. Barnaby’s thistle centauré du solstice
IntroducedIllustrated
Treatment appears in FNA Volume 19. Treatment on page 193. Mentioned on page 183.

Annuals, 10–100 cm. Stems simple or often branched from base, forming rounded bushy plants, gray-tomentose. Leaves gray-tomentose and scabrous to short-bristly; basal and proximal cauline petiolate or tapered to base, usually absent at anthesis, blades 5–15 cm, margins pinnately lobed or dissected; cauline long-decurrent, blades linear to oblong, 1–10 cm, entire. Heads disciform, borne singly or in open leafy arrays, long-pedunculate. Involucres ovoid, 13–17 mm, loosely cobwebby-tomentose or becoming glabrous. Principal phyllaries: bodies pale green, ovate, appendages stramineous to brown, each with palmately radiating cluster of spines, and stout central spine 10–25 mm. Inner phyllaries: appendages scarious, obtuse or abruptly spine tipped. Florets many; corollas yellow, all ± equal, 13–20 mm; sterile florets slender, inconspicuous. Cypselae dimorphic, 2–3 mm, glabrous, outer dark brown, without pappi, inner white or light brown, mottled; pappi of many white, unequal bristles 2–4 mm, fine. 2n = 16.


Phenology: Flowering mostly summer–autumn (Jun–Oct), sometimes year-round in frostfree coastal habitats.
Habitat: Roadsides, fields, pastures, woodlands
Elevation: 0–2000 m

Distribution

V19-226-distribution-map.gif

Introduced; Widely Alta., Man., Ont., Sask., Ariz., Calif., Colo., Conn., Del., Fla., Idaho, Ill., Ind., Iowa, Kans., Ky., Md., Mass., Mich., Minn., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Va., Wash., W.Va., Wis., Wyo., s Europe.

Discussion

Centaurea solstitialis is a serious weed pest, especially in the western United States, where it has invaded millions of acres of rangelands, and it is listed as a noxious weed in eleven western states and two Canadian provinces. It is a strong competitor in infested areas, often forming dense colonies. It is very difficult to control or eradicate once it becomes established. In addition, yellow star-thistle is poisonous to horses; when ingested over a prolonged period it causes a neurological disorder called equine nigropallidal encephalomalacia, or “chewing disease.” Although its bitter taste and spiny heads usually deter grazing animals, horses sometimes will seek it out. Yellow star-thistle tends to spread in rangelands when more palatable plants are consumed.

Selected References

None.

Lower Taxa

None.

... more about "Centaurea solstitialis"
David J. Keil +  and Jörg Ochsmann +
Linnaeus +
Asteraceae tribe Cynareae +
Yellow or Barnaby star-thistle +, St. Barnaby’s thistle +  and centauré du solstice +
Widely Alta. +, Man. +, Ont. +, Sask. +, Ariz. +, Calif. +, Colo. +, Conn. +, Del. +, Fla. +, Idaho +, Ill. +, Ind. +, Iowa +, Kans. +, Ky. +, Md. +, Mass. +, Mich. +, Minn. +, Mo. +, Mont. +, Nebr. +, Nev. +, N.H. +, N.J. +, N.Mex. +, N.Y. +, N.C. +, N.Dak. +, Ohio +, Okla. +, Oreg. +, Pa. +, R.I. +, S.C. +, S.Dak. +, Tenn. +, Tex. +, Utah +, Va. +, Wash. +, W.Va. +, Wis. +, Wyo. +  and s Europe. +
0–2000 m +
Roadsides, fields, pastures, woodlands +
Flowering mostly summer–autumn (Jun–Oct), sometimes year-round in frostfree coastal habitats. +
Introduced +  and Illustrated +
Acosta +, Cnicus +, Grossheimia +, Jacea +  and Leucacantha +
Centaurea solstitialis +
Centaurea +
species +