Helianthus decapetalus
Helianthus occidentalis
hélianthe à dix rayons, thin-leaf sunflower
fewleaf sunflower, naked-stem sunflower, western sunflower
erect, glabrous.
(often reddish) erect, pilose to appressed-hairy proximally.
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 basal; opposite;
petioles 2.5–10 cm;
blades oblong-lanceolate or elliptic to ovate, 5–20 × 1.5–7 cm, bases cuneate, margins entire or serrulate, abaxial faces scabrous to hispidulous, gland-dotted (cauline usually smaller, rarely 2–4 pairs well developed).
2–12 cm (not gland-dotted).
1–14 cm.
cylindric, 9–14 mm diam.
8–12;
laminae 20–25 mm.
8–14;
laminae 18–22 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.
50+;
corollas 4.5–5.5 mm, lobes yellow;
anthers dark brown or black, appendages yellow.
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.
20–25, lanceolate, 4.5–7(–11) × 1.5–2.5 mm, (margins usually ciliate) apices acute to short-acuminate, abaxial faces glabrate to sparsely pilose (hairs moniliform), not gland-dotted.
3–6(–10).
1–4(–12).
3.5–5 mm;
pappi of 2 aristate scales 3–4 mm.
3–4(–5) mm, sparsely villous or glabrate;
pappi of 2 aristate scales 1.5–2.8 mm plus 0–4 deltate scales 0.4–1 mm.
-lucres hemispheric, 12–25 mm diam.
8–10 mm, 3-toothed.
5–7 mm, subentire to 3-toothed (shortly mucronate).
= 34, 68.
= 34 (subspecies unknown).
Helianthus decapetalus
Helianthus occidentalis
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.)
Subspecies 2 (2 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaves entire or nearly so, scabrous or hirsute, rough to touch | subsp. occidentalis |
1. Leaves usually serrate, strigose or glabrous, smooth to touch | subsp. plantagineus |
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