Helianthus decapetalus
Helianthus mollis
hélianthe à dix rayons, thin-leaf sunflower
ashy sunflower, downy sunflower
erect, glabrous.
erect, hirsute to villous.
cauline; opposite (proximal or all) or alternate (distal);
petioles (1–)2–5 cm;
blades (green, 3-nerved distal to bases) lanceolate to ovate, 7–21 × 4–10 cm, bases rounded to cuneate (often shortly decurrent onto petioles), margins usually serrate (moderately to notably in larger leaves), abaxial faces ± scabro-hispidulous, relatively sparsely gland-dotted.
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.
2–12 cm (not gland-dotted).
0.1–15 cm.
broadly hemispheric, 12–25 mm diam.
8–12;
laminae 20–25 mm.
17–22;
laminae 25–30 mm (abaxial faces densely gland-dotted).
40+;
corollas 6.5–7.2 mm, lobes yellow;
anthers usually dark brown to black (rarely reddish brown), appendages dark or reddish brown.
75+;
corollas 6–7.5 mm, lobes yellow;
anthers dark, appendages dark.
20–25 (often reflexed), lance-linear to lanceolate, 11–16 × 2–3 mm (sometimes leaflike, longest surpassing discs by 1/2+ their lengths), (margins ciliate) apices attenuate, abaxial faces strigillose to glabrate, not 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.
3–6(–10).
1–15.
3.5–5 mm;
pappi of 2 aristate scales 3–4 mm.
3.5–4 mm, distally villous;
pappi of 2 aristate scales 2.8–3.2 mm.
-lucres hemispheric, 12–25 mm diam.
8–10 mm, 3-toothed.
(oblanceolate) 9–11 mm, entire (1-toothed, densely hairy, densely gland-dotted).
= 34, 68.
= 34.
Helianthus decapetalus
Helianthus mollis
Helianthus decapetalus is sometimes confused with Heliopsis helianthoides because of shared habitats and superficial similarities. The tetraploid cytotype of H. decapetalus intergrades (and apparently hybridizes) with H. strumosus, particularly in the southern Appalachians; individual specimens can be difficult to place in one or the other species. In addition to morphologic differences, H. decapetalus usually occurs in more mesic habitats, particularly along watercourses; H. strumosus is found in drier sites such as roadside slopes. Helianthus ×multiflorus Linnaeus is a sterile hybrid, often with “doubled” heads (in which disc florets are replaced by ray florets); it is cultivated and is sometimes included within H. decapetalus, e.g., H. decapetalus var. multiflorus (Linnaeus) A. Gray; its parents are H. decapetalus and H. annuus.
(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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