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.
Perennials, 30-150 cm. Stems usually many, loosely gray-tomentose, branches ascending. Leaves loosely gray-tomentose or becoming glabrous, resin-gland-dotted; basal and proximal cauline petiolate, blades 10-15 cm, margins 1-2 times divided into linear or oblong segments; mid and distal cauline smaller, entire or dissected. Heads usually many in open cymiform arrays, pedunculate. Involucres ovoid, 10-13 mm. Phyllaries: bodies pale green or pink tinged, ovate (outer to oblong (inner), with seveal prominent parallel veins, glabrous or finely tomentose, erect appendages, decurrent on distal phyllary margins, dark brown or black, scarious, fringed with slender teeth. Florets 30-40; corollas pink to purple (white), those of sterile florets 15-25 mm, slender or somewhat enlarged, those of fertile florests 12-15 mm. Cypselae whitish or pale brown, 3-3.5 mm, finely hairy; pappi in 1-2 series, of many white, unequal, stiff bristles to 5 mm.
Biennial or short-lived perennial 3-15 dm, sparsely scabrous-puberulent, and with a thin and loose evanescent tomentum; lvs pinnatifid with narrow lobes, or the reduced ones of the infl entire; heads ter minating the numerous branches, constricted upward in life; invol 10-13 mm, its bracts striate, the middle and outer ones with short, dark, pectinate tip; fls pink-purple, the marginal ones enlarged; pappus to 3 mm, or rarely none; 2n=18, 36. Fields, roadsides, and waste places; native of Europe, now commonly established in our range and westward. June-Oct. (C. rhenana; ? C. stoebe L., an older name)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
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