Helianthus decapetalus
Helianthus radula
hélianthe à dix rayons, thin-leaf sunflower
pineland sunflower, rayless sunflower, stiff sunflower
erect, glabrous.
erect, distally densely hispid.
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 obscure (intergrading with blades);
blades obovate to orbiculate, 4.6–14.5 × 2.1–12 cm, bases broadly cuneate to rounded, margins entire or serrulate, abaxial faces strigoso-hispid, not gland-dotted (cauline usually much smaller, alternate distally).
2–12 cm (not gland-dotted).
10–20 cm.
shallowly hemispheric, (15–25 ×) 5–8 mm.
8–12;
laminae 20–25 mm.
0 or 2–8;
laminae (sometimes purplish) 1–2(–10) mm.
40+;
corollas 6.5–7.2 mm, lobes yellow;
anthers usually dark brown to black (rarely reddish brown), appendages dark or reddish brown.
100–150+;
corollas 7–8 mm, lobes reddish;
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.
(often dark purple) 25–33, lanceolate to ovate, 10–14 × 3–5 mm, apices acute to acuminate, abaxial faces hispid or glabrous.
3–6(–10).
usually borne singly.
3.5–5 mm;
pappi of 2 aristate scales 3–4 mm.
3–4 mm, glabrate;
pappi of 2 (often unequal) aristate scales 0.5–2.9 mm.
-lucres hemispheric, 12–25 mm diam.
8–10 mm, 3-toothed.
9–10 mm, subentire to 3-toothed (apices purplish, mucronate).
= 34, 68.
= 34.
Helianthus decapetalus
Helianthus radula
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.)
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