Helianthus tuberosus
Helianthus mollis
girasole, Jerusalem artichoke, Jerusalem sunflower, topinambour, tuberous sunflower
ashy sunflower, downy sunflower
erect, scabro-hispid to hirsute (sometimes glaucous).
erect, hirsute to villous.
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).
mostly cauline; mostly opposite (sometimes alternate among heads);
sessile;
blades (ashy or gray-green, 3-nerved distal to bases) lanceolate to broadly ovate, 5.5–14.5 × 1.8–6.5 cm, bases rounded to cordate, margins entire or serrulate, abaxial faces hispid to tomentose, gland-dotted.
1–15 cm.
0.1–15 cm.
hemispheric, (10–25 ×) 8–12 mm.
broadly hemispheric, 12–25 mm diam.
10–20;
laminae 25–40 mm.
17–22;
laminae 25–30 mm (abaxial faces densely gland-dotted).
60+;
corollas 6–7 mm, lobes yellow;
anthers dark brown or black, appendages dark or yellowish.
75+;
corollas 6–7.5 mm, lobes yellow;
anthers dark, 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.
30–40, lanceolate, (5–)10–16 × 2–3.5 mm, apices usually acute, sometimes acuminate, abaxial faces densely hispid to villous or tomentose, densely gland-dotted.
3–15.
1–15.
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.
3.5–4 mm, distally villous;
pappi of 2 aristate scales 2.8–3.2 mm.
8–9 mm, 3-toothed (apices hairy).
(oblanceolate) 9–11 mm, entire (1-toothed, densely hairy, densely gland-dotted).
= 102.
= 34.
Helianthus tuberosus
Helianthus mollis
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 mollis is introduced in Ontario and adventive in the eastern United States (e.g., Maine), where it is continuing to spread, particularly along roads. Natural hybrids between H. mollis and H. occidentalis have been named H. cinereus Torrey & A. Gray (R. C. Jackson and A. T. Guard 1957); they differ from H. mollis by having smaller heads with fewer ray florets and narrower leaves with cuneate bases. Hybrids of H. mollis with H. giganteus have been called H. doronicoides Lamarck (Jackson 1956).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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