Helianthus decapetalus
Helianthus floridanus
hélianthe à dix rayons, thin-leaf sunflower
Florida sunflower
erect, glabrous.
(green) erect, hispid to hispidulous.
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; usually opposite or alternate, rarely whorled;
petioles 0–1 cm;
blades (1- or 3-nerved) lanceolate to elliptic or lance-ovate, 4–15 × 0.5–6 cm, bases rounded to cuneate, margins entire or serrulate (often undulate, often ± revolute), faces ± scabrous to tomentulose and gland-dotted (abaxial) or scabrous (adaxial).
2–12 cm (not gland-dotted).
2–15 cm.
± hemispheric, 12–19 × 7–9 mm.
8–12;
laminae 20–25 mm.
10–20;
laminae 20–25 mm (abaxial faces 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.
90+;
corollas 4–5 mm, lobes usually reddish, sometimes yellow;
anthers dark brown or black, appendages dark (style branches 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.
33–38, lanceolate, 5–9 × 1.5–3 mm, apices (at least outer) obtuse, abaxial faces hispidulous to hispid, gland-dotted.
3–6(–10).
1–6.
3.5–5 mm;
pappi of 2 aristate scales 3–4 mm.
2.5–3 mm, glabrous;
pappi of 2 aristate scales 1.5–2.2 mm.
-lucres hemispheric, 12–25 mm diam.
8–10 mm, 3-toothed.
4.5–6 mm, entire or weakly 3-toothed (apices purplish, glabrate to puberulent, often gland-dotted).
= 34, 68.
= 34.
Helianthus decapetalus
Helianthus floridanus
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 floridanus is similar to and intergrades with H. angustifolius, which has narrower leaves, and H. simulans, which is more robust and has longer leaves without undulate margins.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Go Botany
IL Wildflowers
LA Plants
MD Biodiversity
MI Flora
MO Plants
WildflowerSearch
iNaturalist
USDA Plants Database
