Helianthus decapetalus
Helianthus hirsutus
hélianthe à dix rayons, thin-leaf sunflower
hairy sunflower
erect, glabrous.
erect, hirsute.
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; mostly opposite;
petioles 0.4–2 cm;
blades (3-nerved from bases) lanceolate to ovate, 6.5–18 × 1–8 cm, bases truncate to broadly rounded or cuneate, margins subentire to serrate (flat), abaxial faces ± hirsute, gland-dotted (adaxial not gland-dotted).
2–12 cm (not gland-dotted).
1–5 cm.
hemispheric, 10–25 mm diam.
8–12;
laminae 20–25 mm.
10–15;
laminae 15–20 mm.
40+;
corollas 6.5–7.2 mm, lobes yellow;
anthers usually dark brown to black (rarely reddish brown), appendages dark or reddish brown.
40+;
corollas 5.5–6.5 mm, lobes yellow;
anthers dark brown or black, appendages dark or yellowish.
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.
18–25 (usually loose, spreading, not reflexed), lanceolate, 7–12 × 2.5–3.5 mm, (margins ciliate) apices acute to short-acuminate, abaxial faces not gland-dotted.
3–6(–10).
1–7.
3.5–5 mm;
pappi of 2 aristate scales 3–4 mm.
4–4.5 mm, glabrate or distally puberulent;
pappi of 2 aristate scales 2.5–3.2 mm.
-lucres hemispheric, 12–25 mm diam.
8–10 mm, 3-toothed.
7–10 mm, 3-toothed (apices yellowish, hairy).
= 34, 68.
= 68.
Helianthus decapetalus
Helianthus hirsutus
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 hirsutus is distinguished from H. strumosus by hairy stems and usually yellow (as opposed to dark) anther appendages, and from H. divaricatus by petioles and leaf blades 3-nerved distal to bases. Mexican plants of H. hirsutus are sometimes labeled with the synonymous H. leptocaulis (S. Watson) S. F. Blake, and plants from Mexico and the southwestern United States often have leaf bases cuneate rather than truncate.
(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
KS Wildflowers
MN Wildflowers
