Helianthus giganteus 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 with crown-buds, short rhizomes, and thickened, often fleshy roots; stems 1–3 m, coarsely spreading-hairy to occasionally subglabrous; lvs flat, strongly scabrous above, usually hirsute beneath, ± triplinerved at the base, strongly toothed to subentire, lanceolate, acuminate, 8–20 × 1–3.5 cm, tapering to the short petiole or petiolar base, the upper generally alternate; heads several or many in an open infl; disk yellow, 1.5–2.5 cm wide; invol bracts narrow, thin, green (or dark below), acuminate or attenuate, loose, often conspicuously surpassing the disk, strongly hirsute- ciliate and often hairy on the back; rays 10–20, 1.5–3 cm; 2n=34. Swamps and other moist places; Me. and N.B. to n. S.C. and n. Ga., w. to s. Alta. and Neb. Aug.–Oct. (H. subtuberosus; H. rydbergii, a nw. phase approaching the cordilleran H. nuttallii Torr. & A. Gray)
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Common Names
swamp sunflower