Helianthus decapetalus
Helianthus smithii
hélianthe à dix rayons, thin-leaf sunflower
Smith's sunflower
erect, glabrous.
(usually purplish) erect, glabrous (glaucous).
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.
cauline; opposite (proximal) or alternate;
petioles to 1.3 cm;
blades (light to dark green, 1-nerved) lance-linear to lanceolate, 7–18 × 1–1.8 cm, bases ± cuneate, margins serrulate, abaxial faces ± hispid, gland-dotted.
2–12 cm (not gland-dotted).
3–6 cm.
hemispheric, 5–15 mm diam.
8–12;
laminae 20–25 mm.
6–9;
laminae 10–15 mm.
40+;
corollas 6.5–7.2 mm, lobes yellow;
anthers usually dark brown to black (rarely reddish brown), appendages dark or reddish brown.
25+;
corollas 5.5–6 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.
15–20, lanceolate, 6–9 × 2–2.7 mm, (margins ciliate) apices short-acuminate, abaxial faces glabrous or glabrate, not gland-dotted.
3–6(–10).
1–5.
3.5–5 mm;
pappi of 2 aristate scales 3–4 mm.
2.8–3 mm, glabrate;
pappi of 2 aristate scales 1.5–2 mm.
-lucres hemispheric, 12–25 mm diam.
8–10 mm, 3-toothed.
5.5–6.5 mm, 3-toothed (gland-dotted).
= 34, 68.
= 68.
Helianthus decapetalus
Helianthus smithii
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.)
Of conservation concern.
Helianthus smithii is known from relatively few sites. T. A. Storbeck (1984) concluded that it is a distinct species; he could not rule out the possibility that it might be a hybrid of H. microcephalus and H. strumosus. It may also be an extreme variant of H. strumosus that has relatively narrow leaves and small heads.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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