Helianthus tuberosus
Helianthus giganteus
girasole, hélianthe scrofuleux, Jerusalem artichoke, Jerusalem sunflower, rough sunflower, topinambour, tuberous sunflower
Florida sunflower, giant sunflower, tall sunflower
erect, scabro-hispid to hirsute (sometimes glaucous).
(usually reddish) erect, hairy.
mostly cauline; opposite or alternate proximally, usually alternate distally;
petioles 2–8 cm (often ± winged);
blades (3-nerved from near bases) lanceolate to ovate, 10–23 × 7–15 cm, bases broadly to narrowly cuneate, margins entire or serrate (flat), abaxial faces puberulent or hirsutulous to tomentulose and gland-dotted (abaxial) or ± scabrous (adaxial).
cauline; mostly alternate;
petioles 0–1.2 cm (ciliate);
blades (3-nerved from bases) lanceolate to lance-ovate, 7–20 × 1.2–3.5 cm, bases cuneate, margins serrulate to subentire (± flat), abaxial faces scabrous or ± hirsute, sometimes gland-dotted.
1–15 cm.
8–12 mm.
hemispheric, (10–25 ×) 8–12 mm.
hemispheric, 10–24 mm diam.
10–20;
laminae 25–40 mm.
12–20;
laminae (often pale yellow) 15–25 mm (abaxial faces not gland-dotted).
60+;
corollas 6–7 mm, lobes yellow;
anthers dark brown or black, appendages dark or yellowish.
60+;
corollas 5–6 mm, lobes yellow;
anthers dark brown or black, appendages dark.
(often dark green, drying nearly black) 22–35 (bases appressed, apices ± spreading, sometimes reflexed in fruit), lanceolate, 8.5–15 × 2–4 mm (subequal), (margins ciliate) apices acuminate, abaxial faces hispidulous or puberulent, gland-dotted.
20–25 (loose or spreading), linear, 8–15 × 1.2–2 mm, (margins usually ciliate) apices acute to attenuate, abaxial faces sparsely strigose, not gland-dotted.
3–15.
1–12.
5–7 mm, glabrous or distally hairy;
pappi of 2 aristate scales 1.9–3 mm plus 0–1 deltate scales 0.5–0.8 mm.
3–4 mm, glabrate;
pappi of 2 aristate scales 2.4–3 mm.
8–9 mm, 3-toothed (apices hairy).
7–9 mm, entire or ± 3-toothed (apices acute, hairy).
= 102.
= 34.
Helianthus tuberosus
Helianthus giganteus
Helianthus tuberosus is variable, probably in part stemming from hybridization with other polyploids, including H. pauciflorus, H. resinosus, and H. strumosus. Helianthus tuberosus is so widely spread as a weedy species that its original distribution is difficult to discern. It has been used as a food plant for its tubers by native Americans (although not necessarily domesticated or even cultivated); it has been developed as a crop primarily in Europe, where it has become widely naturalized. The common name Jerusalem artichoke is a misnomer, as explained by C. B. Heiser (1976).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Helianthus giganteus was probably introduced in Newfoundland. It intergrades with H. nuttallii and H. grosseserratus; it is distinctive in its hairy, reddish-colored stems, dark anther appendages, and prominent setae on the petioles. The natural hybrid of H. giganteus with H. grosseserratus has been called H. luxurians E. Watson (R. W. Long 1954). Hybrids of H. giganteus with H. divaricatus have been referred to as H. ambiguus (Torrey & A. Gray) Britton and H. ×divariserratus R. W. Long (Long 1954).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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