Centaurea nigra L.
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Authority
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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Family
Asteraceae
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Scientific Name
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Description
Species Description - Perennial, 2-8 dm, rough-puberulent and sometimes arachnoid when young; lvs entire or toothed, the basal ones broadly oblanceolate or elliptic, entire or toothed to sometimes few-lobed, mostly (1-)1.5-4(-6) cm wide, petiolate, the cauline ones reduced upward and becoming sessile; heads terminating the often numerous branches; invol 12-19 mm, broader than high; appendages of the invol bracts well developed, conspicuously blackish at least in part, the middle and outer deeply and fairly regularly pectinate, the larger ones mostly (3-)4-6 mm long, seldom any of them markedly bifid; fls pink-purple, the marginal ones typically not enlarged; pappus ca 1 mm or less; 2n=22, 44. Fields, roadsides, and waste places; native of Europe, now widely established in s. Can. and n. U.S., s. to Va. and W.Va. July-Oct. Hybridizes with no. 7 [Centaurea jacea L.], producing segregating or stabilized intermediates called C. ×pratensis Thuill., these often approaching C. nigra as to invol, but subradiate as in C. jacea. (C. nigra var. radiata)
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Common Names
black knapweed