Centaurea benedicta |
Centaurea nigrescens |
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blessed knapweed, blessed thistle, chardon bénit |
centaurée noirâtre, short-fringe knapweed, Tyrol knapweed, Tyrol or short-fringe or vochin knapweed |
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Habit | Annuals, to 60 cm. | Perennials, 30–150 cm. |
Stems | often spreading or prostrate, usually branched throughout, usually reddish, ± loosely tomentose. |
1–few, erect or ascending, openly branched distally, villous to scabrous with septate hairs and loosely tomentose, ± glabrate. |
Leaves | mostly cauline, sessile and often short-decurrent or proximal tapering to winged petioles, blades lanceolate to oblanceolate, 6–25 cm, margins coarsely dentate or pinnately lobed, lobes and teeth armed with short, weak spines, faces sparsely to densely hairy with jointed multicellular hairs and slender cobwebby hairs, resin-gland-dotted. |
basal and proximal cauline, petiolate, blades oblanceolate or elliptic, 5–25 cm, margins entire or shallowly dentate to irregularly pinnately lobed; distal cauline sessile, not decurrent, blades linear to lanceolate, gradually smaller, entire or dentate. |
Involucres | ± spheric, 20–40 mm. |
15–18 mm, subcylindric to ovoid or campanulate, usually longer than wide, even when pressed. |
Florets | many; corollas yellow, those of sterile florets linear, 3-lobed, not exceeding disc corollas, very slender, those of disc florets 19–24 mm. |
40–100+, all fertile or peripheral sterile; corollas purple (rarely white), those of sterile florets ± expanded and exceeding corollas of fertile florets, those of fertile florets 15–18 mm. |
Phyllaries | in several series, tightly overlapping, outer ovate with tightly appressed bases and spreading spine tips, inner lanceolate, tipped by pinnately divided spines more than 5 mm. |
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Inner phyllaries | tips truncate, irregularly dentate or lobed. |
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Heads | disciform, borne singly, sessile, each subtended by involucre-like cluster of leaf-like bracts. |
radiant or discoid, in few-headed corymbiform arrays, borne on leafy-bracted peduncles. |
Cypselae | cylindric, slightly curved, 8–11 mm, with 20 prominent ribs, tipped by a 10-dentate rim, glabrous, attachment scars lateral; pappi of 2 series of awns, outer 9–10 mm, smooth or ± roughened, inner 2–5 mm, roughened with short spreading hairs. |
tan, 2.5–3 mm, finely hairy; pappi 0 or of many unequal, sometimes caducous bristles 0.5–1 mm. |
Principal | phyllaries: bodies lanceolate to ovate, loosely tomentose or glabrous, usually not fully covered by narrow appendages, these erect, overlapping, dark brown to black, flat, margins pectinately dissected into 6–8 pairs of wiry lobes. |
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2n | = 22. |
= 22 (Hungary), 44 (Hungary; Italy). |
Centaurea benedicta |
Centaurea nigrescens |
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Phenology | Flowering spring–summer (Apr–Aug). | Flowering summer–fall (Jun–Oct). |
Habitat | Roadsides, fields, waste places, sometimes cultivated | Roadsides, fields, waste areas |
Elevation | 0–1300 m (0–4300 ft) | 0–1000 m (0–3300 ft) |
Distribution |
AL; AR; AZ; CA; CT; FL; GA; IL; MD; NC; NJ; NY; OR; SC; TN; TX; UT; VA; WA; WI; NB; NS; ON; Europe; Asia [Introduced in North America; widely introduced worldwide]
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CA; CT; DE; FL; IL; IN; MA; MO; MT; NH; NJ; NY; OH; OR; PA; RI; VA; VT; WA; WI; WV; WY; BC; ON; QC; Europe [Introduced in North America]
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Discussion | Centaurea benedicta is native to the Mediterranean region and Asia Minor. F. K. Kupicha (1975) recognized two varieties of Cnicus benedictus: var. benedictus and var. kotschyi Boissier. A combination apparently has not been made for var. kotschyi in Centaurea. I have not determined whether one or both races are represented in North American plants of Centaurea benedicta. Blessed thistle is cultivated in many areas of the world as a medicinal herb. The leaves, stems, and flowers are all used in herbal preparations for digestive and liver ailments. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Tyrol knapweed is considered to be a noxious weed in Washington and Oregon. In recent years there has been much controversy regarding the name(s) to be applied to the North American Tyrol knapweeds. The names Centaurea vochinensis, C. nigrescens, and C. dubia have all been used in twentieth-century North American floras, and J. T. Kartesz and C. A. Meacham (1999) have accepted C. transalpina as well. R. J. Moore (1972) tentatively accepted two species, C. nigrescens and C. dubia, placing C. transalpina and C. vochinensis as synonyms through application beneath both species. Moore discussed the considerable similarities and practical difficulties of differentiating the taxa. H. A. Gleason and A. Cronquist (1991) recognized C. dubia as including C. nigrescens and C. vochinensis. E. G. Voss (1972–1996, vol. 3) recognized C. nigrescens as including C. dubia and C. vochinensis. Kartesz and Meacham accept C. nigrescens as a species, including C. vochinensis; they also accept C. transalpina with C. dubia as a synonym. In our investigation of the North American Tyrol knapweeds we have not been able to distinguish more than one (admittedly variable) entity. At the species level the correct name for this taxon is Centaurea nigrescens. Centaurea dubia Suter, sometimes applied to plants that belong here, is not a valid name. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 19, p. 192. | FNA vol. 19, p. 188. |
Parent taxa | Asteraceae > tribe Cardueae > Centaurea | Asteraceae > tribe Cardueae > Centaurea |
Sibling taxa | ||
Synonyms | Cnicus benedictus | C. dubia subsp. nigrescens, C. dubia subsp. vochinensis, C. jacea subsp. nigrescens, C. transalpina, C. vochinensis |
Name authority | (Linnaeus) Linnaeus: Sp. Pl. ed. 2, 2: 1296. (1763) | Willdenow: Sp. Pl. 3: 2288. (1803) |
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