Helianthus bolanderi
Helianthus annuus
Bolander's sunflower, serpentine sunflower
common sunflower, hairy leaf sunflower, sunflower
erect, hispid to hirsute.
erect, usually hispid.
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.
mostly cauline; mostly alternate;
petioles 2–20 cm;
blades lance-ovate to ovate, 10–40 × 5–40 cm, bases cuneate to subcordate or cordate, margins serrate, abaxial faces usually ± hispid, sometimes gland-dotted.
3–13 cm.
2–20 cm.
hemispheric, 17–25 mm diam.
hemispheric or broader, 15–40(–200+) mm diam.
12–17;
laminae 14–20 mm.
(13–)17–30(–100+);
laminae 25–50 mm.
75+ (discs usually 2+ cm diam.);
corollas 5–7 mm, lobes usually reddish;
anthers dark, appendages dark (style branches reddish).
150+(–1000+);
corollas 5–8 mm (throats ± bulbous at bases), lobes usually reddish, sometimes yellow;
anthers brownish to black, appendages yellow or dark (style branches yellow).
10–18, usually lanceolate to lance-ovate, 9–27 × (3–)3.5–5 mm (often surpassing discs), apices gradually attenuate, abaxial faces hirsute.
20–30(–100+), ovate to lance-ovate, 13–25 × (3–)5–8 mm, (margins usually ciliate) apices abruptly narrowed, long-acuminate, abaxial faces usually hirsute to hispid, rarely glabrate or glabrous, usually gland-dotted.
1–3.
1–9.
3.5–4.5 mm, glabrate;
pappi of 2 lanceolate scales 1.7–3 mm.
(3–)4–5(–15) mm, glabrate;
pappi of 2 lanceolate scales 2–3.5 mm plus 0–4 obtuse scales 0.5–1 mm.
9.5–10.5 mm, 3-toothed (middle teeth subulate, surpassing discs, apices glabrous).
9–11 mm, 3-toothed (middle teeth long-acuminate, glabrous or hispid).
= 34.
= 34.
Helianthus bolanderi
Helianthus annuus
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 annuus is widely distributed, including weedy, cultivated, and escaped plants. It is the only native North American species to become a major agronomic crop. Despite its considerable variability, attempts have failed to produce a widely adopted infraspecific system of classification. Forms with red-colored ray laminae, known from cultivation and occasionally seen escaped, trace their ancestry to a single original mutant plant. It hybridizes with many of the other annual species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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