Helianthus annuus
Helianthus atrorubens
common sunflower, hairy leaf sunflower, sunflower
purpledisc sunflower, purpledisk sunflower
erect, usually hispid.
erect, proximally villous to strigoso-hispid, distally hispid or glabrate.
mostly cauline; mostly alternate;
petioles 2–20 cm;
blades lance-ovate to ovate, 10–40 × 5–40 cm, bases cuneate to subcordate or cordate, margins serrate, abaxial faces usually ± hispid, sometimes gland-dotted.
mostly basal; opposite;
petioles 4–25 cm (usually winged at least 1/2 their lengths);
blades lanceolate to ovate, 7–26 × 3–10 cm, bases broadly cuneate to nearly truncate (often decurrent onto petioles), margins serrate to crenate, abaxial faces strigoso-hispid (hairs of midribs1+ mm), not gland-dotted (cauline to 8 pairs proximal to heads, ovate to elliptic, smaller).
2–20 cm.
0.3–17 cm.
hemispheric or broader, 15–40(–200+) mm diam.
broadly hemispheric, 9–16 mm diam.
(13–)17–30(–100+);
laminae 25–50 mm.
10–15;
laminae 15–22 mm (abaxial faces not gland-dotted).
150+(–1000+);
corollas 5–8 mm (throats ± bulbous at bases), lobes usually reddish, sometimes yellow;
anthers brownish to black, appendages yellow or dark (style branches yellow).
75+;
corollas 4–6 mm, lobes reddish;
anthers dark, appendages dark (style branches yellow).
20–30(–100+), ovate to lance-ovate, 13–25 × (3–)5–8 mm, (margins usually ciliate) apices abruptly narrowed, long-acuminate, abaxial faces usually hirsute to hispid, rarely glabrate or glabrous, usually gland-dotted.
15–22, broadly ovate to oblong, 7–9 × 4–5 mm, (margins ciliolate) apices obtuse to acute, sometimes mucronate, abaxial faces usually glabrous.
1–9.
(1–)3–15+.
(3–)4–5(–15) mm, glabrate;
pappi of 2 lanceolate scales 2–3.5 mm plus 0–4 obtuse scales 0.5–1 mm.
2.8–3 mm, glabrous or distally puberulent;
pappi of 2 aristate scales 2.5–2.8 mm.
9–11 mm, 3-toothed (middle teeth long-acuminate, glabrous or hispid).
4–5.5 mm, ± 3-toothed to entire.
= 34.
= 34.
Helianthus annuus
Helianthus atrorubens
Helianthus annuus is widely distributed, including weedy, cultivated, and escaped plants. It is the only native North American species to become a major agronomic crop. Despite its considerable variability, attempts have failed to produce a widely adopted infraspecific system of classification. Forms with red-colored ray laminae, known from cultivation and occasionally seen escaped, trace their ancestry to a single original mutant plant. It hybridizes with many of the other annual species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Helianthus atrorubens and H. silphioides form a morphologically similar pair of species that share the distinctive feature of relatively broad, tightly appressed phyllaries with apices obtuse to acute. Helianthus atrorubens has a more easterly geographic distribution along the Piedmont and the Atlantic coastal plain and the southern Appalachian Mountains; distribution of H. silphioides is centered in the Ozark region. In general, H. silphioides differs in its usually well developed cauline leaves, and basal leaves with winged petioles that are less than half the total lengths. Involucres with phyllaries tightly appressed are also observed in H. occidentalis and H. pauciflorus subsp. pauciflorus, which differs in having the phyllary apices acute to acuminate as well as in usually having abaxial faces of leaves and ray laminae densely gland-dotted.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
- Local floras:
BC, 
CA, 
OR, 
WA - Local Web sites: CalFlora, CalPhotos,
Flora NW, 
Go Botany, 
IL Wildflowers, 
KS Wildflowers, 
LA Plants, 
MD Biodiversity, 
MI Flora, 
MN Wildflowers, 
MO Plants, 
PNW Herbaria, 
SW CO Wildflowers, Turner Photog. 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
