Centaurea calcitrapa |
Centaurea montana |
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caltrops, centaurée chausse-trappe, chausse-trappe, purple knapweed, purple star-thistle, red star-thistle |
Bachelor's button, centaurée des montagnes, montane starthistle, mountain bluet, mountain bluet knapweed, mountain cornflower, mountain cornflower or bluet, mountain knapweed, perennial cornflower |
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Habit | Annuals, biennials, or short-lived perennials, 20–100 cm. | Perennials, 25–80 cm, from rhizomes or stolons. |
Stems | 1–several, often forming rounded mounds, puberulent to loosely tomentose. |
1–several, erect, simple or sparingly branched, villous with septate hairs and thinly arachnoid-tomentose with long, simple hairs. |
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. |
thinly villous and ± tomentose, glabrate; proximal leaves winged-petiolate, blades 10–30 cm, margins entire or remotely dentate to pinnately lobed; mid and distal leaves sessile, blades decurrent, ovate to oblong or lanceolate, entire or remotely denticulate. |
Involucres | ovoid, 15–20 × 6–8 mm. |
ovoid to ± campanulate, 20–25 mm. |
Florets | 25–40; corollas purple, all ± equal, 15–24 mm; sterile corollas slender. |
35–60+; sterile florets 10–20, corollas blue (white, purple, or pink), 2.5–4.5 cm, corolla tube elongate. |
Disc florets | 25–40+; corollas purple, ca. 20 mm; anthers dark blue-purple. |
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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. |
radiant, borne singly or in few-headed corymbiform arrays; (peduncles to 7 cm). |
Cypselae | white or brown-streaked, 2.5–3.4 mm, glabrous; pappi 0. |
± brown, 5–6 mm, sericeous; pappi of bristles 0.5–1.5 mm. |
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. |
phyllaries: bodies greenish, ovate to lanceolate, scarious-margined, appendages appressed, brown to black, unarmed, decurrent on phyllary margins, pectinate-fringed, puberulent; innermost phyllaries sometimes unappendaged. |
2n | = 20. |
= 24 (Germany), 40 (Russia), 44 (France). |
Centaurea calcitrapa |
Centaurea montana |
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Phenology | Flowering summer–autumn (Jun–Nov). | Flowering summer (Jun–Aug). |
Habitat | Pastures, fields, roadsides | Escaped from cultivation, roadsides, woodlands, sagebrush scrub |
Elevation | 0–1700 m (0–5600 ft) | 0–1400 m (0–4600 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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AK; ID; ME; MI; MN; MT; NH; NY; OR; PA; UT; WA; WI; BC; NB; NF; ON; QC; SPM; Europe [Introduced in North America]
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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.) |
Centaurea montana is a very handsome plant, native to the mountains of Europe, now widely cultivated as an ornamental. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 19, p. 191. | FNA vol. 19, p. 185. |
Parent taxa | Asteraceae > tribe Cardueae > Centaurea | Asteraceae > tribe Cardueae > Centaurea |
Sibling taxa | ||
Name authority | Linnaeus: Sp. Pl. 2: 917. (1753) | Linnaeus: Sp. Pl. 2: 911. (1753) |
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