Helianthus bolanderi
Helianthus giganteus
Bolander's sunflower, serpentine sunflower
giant sunflower, hélianthe géant, tall sunflower
erect, hispid to hirsute.
(usually reddish) erect, hairy.
mostly cauline; mostly alternate;
petioles 1–4 cm;
blades lance-linear or lance-ovate to ovate, 3–15 × 2–6 cm, bases cuneate to truncate, margins usually serrate, abaxial faces sparsely hirsute, gland-dotted.
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.
3–13 cm.
8–12 mm.
hemispheric, 17–25 mm diam.
hemispheric, 10–24 mm diam.
12–17;
laminae 14–20 mm.
12–20;
laminae (often pale yellow) 15–25 mm (abaxial faces not gland-dotted).
75+ (discs usually 2+ cm diam.);
corollas 5–7 mm, lobes usually reddish;
anthers dark, appendages dark (style branches reddish).
60+;
corollas 5–6 mm, lobes yellow;
anthers dark brown or black, appendages dark.
10–18, usually lanceolate to lance-ovate, 9–27 × (3–)3.5–5 mm (often surpassing discs), apices gradually attenuate, abaxial faces hirsute.
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.
1–3.
1–12.
3.5–4.5 mm, glabrate;
pappi of 2 lanceolate scales 1.7–3 mm.
3–4 mm, glabrate;
pappi of 2 aristate scales 2.4–3 mm.
9.5–10.5 mm, 3-toothed (middle teeth subulate, surpassing discs, apices glabrous).
7–9 mm, entire or ± 3-toothed (apices acute, hairy).
= 34.
= 34.
Helianthus bolanderi
Helianthus giganteus
Helianthus bolanderi and H. exilis form a closely related pair of sister species that share the distinctive feature of having the middle teeth of the paleae glabrous and relatively elongated, surpassing the disc florets. As treated here, H. bolanderi corresponds to the “valley weed race” (C. B. Heiser 1949; L. H. Rieseberg et al. 1988); it is separated from the “serpentine foothill race,” here recognized as H. exilis. Heiser proposed that H. bolanderi originated through hybridization between H. annuus and H. exilis; molecular studies by Rieseberg et al. do not support this scheme. In an ironic twist, it appears that H. bolanderi may be undergoing “genetic assimilation” through hybridization with H. annuus (S. E. Carney et al. 2000).
(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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