Centaurea stoebe
Centaurea nigrescens
spotted knapweed
centaurée noirâtre, short-fringe knapweed, Tyrol knapweed, Tyrol or short-fringe or vochin knapweed
1–few, erect or ascending, openly branched distally, villous to scabrous with septate hairs and loosely tomentose, ± glabrate.
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.
15–18 mm, subcylindric to ovoid or campanulate, usually longer than wide, even when pressed.
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.
tips truncate, irregularly dentate or lobed.
radiant or discoid, in few-headed corymbiform arrays, borne on leafy-bracted peduncles.
tan, 2.5–3 mm, finely hairy;
pappi 0 or of many unequal, sometimes caducous bristles 0.5–1 mm.
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.
= 22 (Hungary), 44 (Hungary; Italy).
Centaurea stoebe
Centaurea nigrescens
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.)
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.)
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