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..
Senecio frigidus Less. Linnaea 6: 239. 1831.
Perennial, more or less tomentose, or becoming glabrous when old; stem slender, 6'-12' high, bearing a solitary head (rarely 2 or 3) 1/2'-1' broad. Basal and lower leaves spatulate or obovate, l'-2' long, petioled, obtuse, repand-dentate or entire; stem leaves oblong to linear-lanceolate, obtuse or acute, sessile, mostly entire, smaller; involucre broadly campanulate, about 7" high, its bracts lanceolate, acute, with no exterior smaller ones; rays 10-16, 6"-10" long, 3-toothed, linear-oblong, or cuneate at the base; achenes glabrous or sparingly pubescent; pappus white.
Labrador and arctic America to Alaska. Also in northeastern Asia. Summer.
Senecio Jacobaea L. Sp. Pl. 870. 1753.
Perennial by short thick rootstocks, somewhat woolly, or glabrous; stems stout, simple, or branched above, 2°-4° high, very leafy. Stem leaves 2-3-pinnatifid, 2'-8' long, the lower petioled, the upper sessile, the lobes oblong-cuneate, dentate or incised; basal leaves lyrate-pinna-tifid; heads very numerous, 6"-8" broad, short-peduncled in large compact corymbs; involucre narrowly campanulate, about 2 1/2" high, its bracts linear-lanceolate, acute, green, or tipped with black, usually with a few subulate outer ones; rays 12-15; achenes of the disk-flowers pubescent, those of the rays glabrous; pappus white.
In waste places, Newfoundland and Nova Scotia to Maine and Ontario, and in ballast about New York and Philadelphia. Adventive from Europe. Stave-wort. Cankerweed. Kettle-dock. St. James'-wort. Felonweed. Fairies'-horse. Ragweed. Saracen's-com-pass. July-Sept.
Senecio antennariifolius Britton, in Britt. & Brown, III. Fl. 3: 478. 1898.
Perennial, tufted in mostly large clumps; stems slender, 8'-18' high, loosely white-woolly. Leaves nearly all basal, commonly numerous, oval to spatulate, angulately few-toothed or entire, mostly obtuse, narrowed into a petiole as long as the blade or longer, densely white-tomentose beneath, green and finally glabrous above, 1'-2 1/2' long; stem leaves small, spatulate, laciniate, or the upper narrowly linear and entire; heads several, corymbose, slender-peduncled, rathed less than 1' broad; rays golden-yellow, showy; involucre 3" high, white-woolly; achenes glandular-pubescent.
Stony hillsides, mountains of Virginia and West Virginia. May-June.
S. canus Hook. Fl. Bor. Am. 1: 333. pl. 116. 1833.
Perennial, densely and persistently white-tomentose to the inflorescence; stems slender, usually tufted, 6'-18' high. Basal and lower leaves spatulate or oval, entire, or rarely somewhat repand, very obtuse, l'-2' long, narrowed into petioles; upper leaves oblong or spatulate, obtuse or acute, mostly sessile, smaller, entire or dentate; heads several or numerous, 8"-10" broad, usually slender-peduncled; involucre campanulate, or at first short-cylindric, about 5" high, its bracts linear-lanceolate, acute, sparingly tomentose, or glabrate, usually with no exterior smaller ones; rays 8-12; achenes glabrous, at least below; pappus white.
In dry soil, Manitoba to North Dakota, Nebraska, west to British Columbia and California. Recorded from Minnesota. May-Aug.