Helianthus decapetalus
Helianthus ×laetiflorus
hélianthe à dix rayons, thin-leaf sunflower
cheerful sunflower, hélianthe à belles fleurs, mountain sunflower
erect, glabrous.
erect, slightly hairy.
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.
basal and cauline; mostly opposite;
petioles 1–5 cm;
blades lanceolate to lance-ovate, 10–25 × 2–8 cm, bases cuneate, margins serrulate to serrate, abaxial faces sparsely hispid, gland-dotted.
2–12 cm (not gland-dotted).
7–14 cm.
hemispheric, 14–18 mm diam.
8–12;
laminae 20–25 mm.
15–20;
laminae 25–37 mm.
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 7–7.5 mm, lobes reddish (at least at tips);
anthers dark, appendages dark to yellowish (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.
25–35, oblong-lanceolate, 7–12 × 3–3.5 mm (strongly unequal), apices acuminate, abaxial faces usually puberulent, gland-dotted.
3–6(–10).
3–6.
3.5–5 mm;
pappi of 2 aristate scales 3–4 mm.
(seldom formed) 4–5 mm, glabrate;
pappi of 2 aristate scales 2.5–3.5 mm.
-lucres hemispheric, 12–25 mm diam.
8–10 mm, 3-toothed.
9–10 mm, entire or 3-toothed (apices reddish).
= 34, 68.
= 102.
Helianthus decapetalus
Helianthus ×laetiflorus
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 ×laetiflorus is introduced in Ontario, Newfoundland, and probably in Quebec; it was excluded from British Columbia by G. W. Douglas et al. (1989–1994, vol. 1); and it was reported in New Brunswick by H. R. Hinds (2000).
Plants called Helianthus ×laetiflorus are usually interpreted to be hybrids and backcrosses of H. tuberosus and H. pauciflorus; they are widely cultivated and often escape. An alternative treatment has been to use the name H. laetiflorus for plants that are treated here as H. pauciflorus, sometimes with infraspecific taxa.
Helianthus atrorubens Lamarck 1789, not Linnaeus 1753, has been applied to plants here called H. ×laetiflorus.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Go Botany
LA Plants- Local floras:
BC - Local Web sites:
Flora NW, 
IL Wildflowers, 
KS Wildflowers, 
MD Biodiversity, 
MI Flora, 
MN Wildflowers, 
MO Plants, 
PNW Herbaria 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
