Centaurea calcitrapa |
Centaurea stoebe |
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caltrops, centaurée chausse-trappe, chausse-trappe, purple knapweed, purple star-thistle, red star-thistle |
spotted knapweed |
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Habit | Annuals, biennials, or short-lived perennials, 20–100 cm. | |
Stems | 1–several, often forming rounded mounds, puberulent to loosely tomentose. |
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Leaves | puberulent to loosely gray-tomentose, becoming ± glabrous, minutely resin-gland-dotted; proximal leaves petiolate, blades 10–20 cm, 1–3 times pinnately dissected, rosette with central cluster of spines; mid sessile, not decurrent, blades ovate, usually less than 10 cm, narrowly lobed; distal blades linear to oblong, entire to shallowly lobed. |
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Involucres | ovoid, 15–20 × 6–8 mm. |
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Florets | 25–40; corollas purple, all ± equal, 15–24 mm; sterile corollas slender. |
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Inner phyllaries | appendages truncate, spineless. |
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Heads | disciform, borne singly or in leafy cymiform arrays, sessile or short-pedunculate. |
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Cypselae | white or brown-streaked, 2.5–3.4 mm, glabrous; pappi 0. |
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Principal | phyllaries: bodies greenish or stramineous, ovate, scarious-margined, appendages stramineous, spiny fringed at base, each tipped by a stout spreading spine 10–25 mm. |
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2n | = 20. |
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Centaurea calcitrapa |
Centaurea stoebe |
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Phenology | Flowering summer–autumn (Jun–Nov). | |
Habitat | Pastures, fields, roadsides | |
Elevation | 0–1700 m (0–5600 ft) | |
Distribution |
AL; AZ; CA; DC; FL; GA; IA; IL; MA; MD; NJ; NM; NY; OR; PA; UT; VA; WA; ON; Europe; Africa
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AL; AR; AZ; CA; CO; CT; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OR; PA; RI; SC; SD; TN; UT; VA; VT; WA; WI; WV; WY; AB; BC; NB; NS; ON; QC; Europe
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Discussion | Centaurea calcitrapa is native to southern Europe and northern Africa. It is listed as a noxious weed in Arizona, California, Nevada, New Mexico, Oregon, and Washington. These plants are unpalatable and increase on rangelands as more desirable forage plants are consumed. Dense stands are impenetrable because of the vicious spines on the mature involucres. Centaurea ×pouzinii de Candolle, an apparently stabilized hybrid between Centaurea aspera (2n = 22) and C. calcitrapa (2n = 20), has been reported from California. A chromosome count of 2n = 42 has been reported from California material of this nothospecies (A. M. Powell et al. 1974). Centaurea ×pouzinii can be distinguished from C. calcitrapa by its shorter spines and by cypselae with a short pappus. Reports of C. calcitrapoides Linnaeus from North America are apparently based on this hybrid. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Subspecies 3 (1 in the flora). Native to southeastern Europe, Centaurea stoebe has been introduced to the whole of Europe, as far north as southern Sweden. The nomenclature of Centaurea stoebe in the broad sense has been a source of confusion in European literature for about 200 years. The names used in that group (C. stoebe, C. rhenana, C. maculosa, C. biebersteinii) have been applied to different taxa by different authors with varying circumscriptions. Different species concepts were used in western and eastern Europe. Unfortunately this fact was not taken into account properly in the treatment by J. Dostál (1976). Recent studies have shown that the American plants are identical with plants introduced to the whole of Europe (J. Ochsmann 2001). Subsp. micranthos, a tetraploid perennial, is clearly distinct from the diploid, biennial plants native to central Europe known as C. stoebe Linnaeus subsp. stoebe, C. rhenana Boreau, or C. maculosa Lamarck. In most American literature the name Centaurea maculosa Lamarck has been misapplied to C. stoebe subsp. micranthos. W. A. Weber (1987, 1990) treated this taxon as Acosta maculosa (Lamarck) Holub. The treatment of about 100 species of Centaurea sect. Acrolophus Cassini as the genus Acosta by J. Holub (1972) and others is supported by neither morphologic nor molecular characters and is not widely accepted in Europe. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 19, p. 191. | FNA vol. 19, p. 189. |
Parent taxa | Asteraceae > tribe Cardueae > Centaurea | Asteraceae > tribe Cardueae > Centaurea |
Sibling taxa | ||
Subordinate taxa | ||
Name authority | Linnaeus: Sp. Pl. 2: 917. (1753) | Linnaeus: Sp. Pl. 2: 914. (1753) |
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