Helianthus tuberosus
Helianthus divaricatus
girasole, Jerusalem artichoke, Jerusalem sunflower, topinambour, tuberous sunflower
woodland sunflower
erect, scabro-hispid to hirsute (sometimes glaucous).
erect, usually glabrous, rarely ± hairy (often glaucous).
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; opposite;
sessile;
blades (light to dark green, sometimes whitish abaxially, 3-nerved at bases) lanceolate to lance-ovate, 6–15 × 1–5 cm, bases rounded to cordate, margins subentire to serrate, abaxial faces sparsely hispid to hispidulous, gland-dotted.
1–15 cm.
0.5–9 cm.
hemispheric, (10–25 ×) 8–12 mm.
hemispheric, 10–15 mm diam.
10–20;
laminae 25–40 mm.
8–12;
laminae 15–30 mm.
60+;
corollas 6–7 mm, lobes yellow;
anthers dark brown or black, appendages dark or yellowish.
40+;
corollas 4.2–5.5 mm, lobes yellow;
anthers usually dark brown to black, appendages yellow.
(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.
18–25, lanceolate, lance-linear, or lance-ovate, 6–12 × 2–2.5 mm, (margins ciliate) apices acuminate to attenuate, abaxial faces hispidulous to glabrate, not gland-dotted.
3–15.
1–10.
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.
3–3.6 mm, glabrate;
pappi of 2 aristate scales 2.2–2.5 mm.
8–9 mm, 3-toothed (apices hairy).
5–8 mm, 3-toothed (apices ciliate).
= 102.
= 34.
Helianthus tuberosus
Helianthus divaricatus
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.)
One of the earlier flowering perennial Helianthus, H. divaricatus resembles the tetraploid H. hirsutus but differs by its usually glabrous and often glaucous stems, sessile or subsessile leaves, and smaller reproductive organs (disc corollas, paleae, cypselae). Plants from the Ozark region of Arkansas have larger leaves and heads and may represent a polyploid form of H. divaricatus. Natural hybrids with H. microcephalus have been named H. glaucus Small (D. M. Smith and A. T. Guard 1958). Hybrids with other species differ from H. divaricatus in having short but distinct petioles, hairy stems, leaves with more rounded bases, and primary lateral leaf veins diverging in a subopposite manner distal to bases, rather than being strictly opposite and basal.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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