This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Centaurea Jacea L. Sp. Pl. 914. 1753.
Perennial, 2° high or less. Leaves entire or denticulate, rarely lobed; heads l'-1 1/2' broad; involucre globular to ovoid, its bracts closely imbricated, brown or with brown backs, the outer ones pale brown with fimbriate appendages, the middle ones lacerate, the inner entire or nearly so, dark brown; marginal flowers neutral with enlarged radiant corolla-limbs; achenes obscurely 4-sided; pappus none, or a minute crown.
In waste places, northern New York, Vermont and Massachusetts, and in ballast about eastern seaports. Also in British Columbia. Fugitive from Europe. June-Sept.
ten aurea nigra L. Sp. Pl. 911. 1753.
Perennial, scabrous or pubescent; stem stiff, branched, 1°-2° high. Lower and basal leaves spatulate or oblong, acutish, entire, denticulate, dentate or lobed, not pinnatifid, 3'-6' long, narrowed into long petioles; upper leaves oblong or lanceolate, sessile, or partly clasping, entire or nearly so; heads rarely 1' broad, bracted by the small, uppermost leaves; involucre globose, its bracts lanceolate or ovate-lanceolate, closely imbricated, tipped with brown fimbriate appendages, or the uppermost merely lacerate; flowers rose-purple, all perfect, the marginal ones usually not at all enlarged, or sometimes radiant; achenes slightly 4-sided; pappus none, or a ring of minute scales.
In waste places and fields, Newfoundland to Ontario, New Jersey and Pennsylvania. Naturalized from Europe. Among many other English names are iron-head or -weed, club-weed, matfelon, hurt-sickle, tassel, horse-knobs; crop-, knob-, bole- or button-weed; loggerheads, lady's-cushion, blue-tops, hard-weed, bullweed, sweeps, bachelor's-buttons. July-Sept.
C. Scabiosa L. Sp. Pl. 913. 1753.
Slightly pubescent or villous, perennial; stem simple or branched, about 2° high. Leaves all pinnatifid, the lower and basal ones petioled, often 6' long, the upper sessile and much smaller; heads about 2' broad, on bracted peduncles 1'-4' long; involucre ovoid, its bracts all pectinate to or below the middle, and blackish-margined, the outer ovate, the inner oblong; corolla purple, the outer ones enlarged and neutral; pappus of stiff bristles, about as long as the achene.
Waste grounds and fields, Quebec and Ontario to Ohio. Naturalized from Europe. July-Sept.
C. vochinensis Bernh.; Reichenb. Icon. Fl. Germ. 15: 15. 1853.
Perennial, roughish, branched, 20 high or less. Leaves firm in texture, the basal and lower ones dentate or lyrate, 3-5' long, the upper lanceolate to oblong-lanceolate, few-toothed or entire; heads about 1 1/2' broad; involucre ovoid-cylindric, about 8" high, its faintly nerved bracts pectinate at the brownish tip, the lower short, ovate, the upper elongated; flowers rose-purple, the margined ones radiant.
Waste grounds, Ontario to Massachusetts and southern New York. Naturalized from Europe. Aug.-Oct.