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..
Helianthus laetiflorus Pers. Syn. 2: 476. 1807.
Perennial; stem scabrous or hispid, leafy, 4°-8° high. Leaves oval-lanceolate or ovate-lanceolate, short-peti-oled, 3-nerved, rough on both sides, narrrowed at the base, acute or acuminate at the apex, serrate or serrulate, 4-10' long, 1/2'-1 1/2' wide, the upper often alternate; heads usually several, 2-4' broad, mostly short-peduncled; bracts of the hemispheric involucre ovate-lanceolate, or oblong-lanceolate, imbricated in only 2 or 3 series, ciliate, otherwise nearly glabrous, appressed or but little spreading, shorter than or equalling the yellow disk; rays 15-25, showy; chaff of the receptacle entire, or sometimes 3-toothed.
H. tomentosus Michx. Fl. Bor. Am. 2: 141. 1803.
Perennial; stem stout, hirsute or hispid, especially above, branched, 4°-10° high. Leaves rather thin, ovate, or the lower oblong, mostly alternate, 3-ribbed above the base, gradually or abruptly contracted into margined petioles, rough above, softly villous-pubes-cent beneath, sparingly serrate, the lower often 1° long and 4' wide; heads commonly several or numerous, 3'-4' broad; involucre hemispheric, its bracts imbricated in many series, linear-lanceolate, long-acuminate, squarrose, densely hirsute and ciliate, usually longer than the broad yellowish disk; chaff of the receptacle and lobes of the disk corolla pubescent; pappus of 2 subulate awns.
In dry soil, Virginia to Georgia and Alabama. Reported from Illinois, probably erroneously. Aug.-Oct.
Helianthus tuberosus L. Sp. Pl. 905. 1753. Helianthus tuberosus subcanescens A. Gray, Syn. Fl. 1: Part 2, 280. 1884.
Perennial by fleshy thickened rootstocks, bearing tubers; stems hirsute or pubescent, branched above, 6°-12° high. Leaves ovate or ovate-oblong, rarely ovate-lanceolate, firm, 3-nerved near the base, narrowed, or the lower rounded, truncate or subcordate at the base, acuminate at the apex, rather long-petioled, scabrous above, finely pubescent or canes-cent beneath, serrate, 4'-8' long, 1 1/2'-3' wide, the upper alternate, the lower opposite; heads several or numerous, 2'-31/2' broad; involucre hemispheric, its bracts lanceolate, acuminate, hirsute or ciliate, squarrose; disk yellow; rays 12-20; chaff of the receptacle acute and pubescent at the summit; achenes pubescent.
In moist soil, Nova Scotia and Ontario to Manitoba, Georgia and Arkansas and Kansas. Often occurs along roadsides in the east, a relic of cultivation by the aborigines. Now extensively grown for its edible tubers. Canada potato. Girasole. Topinambour. Sept.-Oct.