Helianthus laciniatus
Helianthus giganteus
alkali sunflower
giant sunflower, hélianthe géant, tall sunflower
erect, usually strigose or hispid to glabrate.
(usually reddish) erect, hairy.
cauline; opposite or alternate;
sessile;
blades (green or grayish, 1- or 3-nerved) lanceolate, 5–9 × 0.5–3.5 cm, bases ± cuneate, margins entire or irregularly toothed to lobed, faces strigose to strumose, gland-dotted (adaxial sometimes glaucous).
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.
4–13 cm.
8–12 mm.
hemispheric, 10–24 mm diam.
hemispheric, 10–24 mm diam.
14–20;
laminae ca. 8–11 mm.
12–20;
laminae (often pale yellow) 15–25 mm (abaxial faces not gland-dotted).
40+;
corollas 4.8–5.8 mm, lobes reddish;
anthers purplish, appendages reddish (style branches yellow).
60+;
corollas 5–6 mm, lobes yellow;
anthers dark brown or black, appendages dark.
16–21, lanceolate, 6–7.5 × 1.8–2.5 mm (often subequal), (margins ciliate) apices acute, abaxial faces hispidulous or strigose to glabrate, 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.
1–9.
1–12.
2.7–3.5 mm, glabrate;
pappi of 2(–3) aristate scales 1.4–2.5 mm.
3–4 mm, glabrate;
pappi of 2 aristate scales 2.4–3 mm.
7–7.8 mm, entire or 3-toothed (apices obtuse to acute, hispid-ciliate to glabrate).
7–9 mm, entire or ± 3-toothed (apices acute, hairy).
= 34.
= 34.
Helianthus laciniatus
Helianthus giganteus
Helianthus laciniatus reaches the northern extent of its range in New Mexico and Texas; it is relatively common in the Chihuahuan Desert areas of Mexico. It is similar to H. ciliaris; it usually has hairy stems as well as denser leaf indument that includes a greater number of subsessile, glandular hairs.
(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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