Helianthus annuus
Helianthus schweinitzii
common sunflower, hairy leaf sunflower, sunflower
Schweinitz's sunflower
erect, usually hispid.
(often reddish, leafy) erect, ± strigose proximally, strigose or glabrous distally.
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.
cauline; opposite (proximal) or alternate;
petioles 0–1 cm;
blades (light to dark green, 3-nerved distal to bases) lanceolate to lance-linear, 6–18 × 1–2 cm, bases cuneate, margins entire or subentire (revolute), faces hirsute to tomentose and gland-dotted (abaxial) or scabrous (adaxial).
2–20 cm.
1.5–8 cm (not gland-dotted).
hemispheric or broader, 15–40(–200+) mm diam.
hemispheric, 9–10(–16) mm diam.
(13–)17–30(–100+);
laminae 25–50 mm.
8–15;
laminae 15–22 mm (abaxial faces 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).
40+;
corollas 5–6 mm, lobes yellow;
anthers dark brown to black, appendages dark or reddish brown.
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.
16–20 (reflexed or loose), lanceolate or lance-ovate, 5–7 × 1.5–2.3 mm, apices acute to acuminate, abaxial faces hirsute (proximally) to glabrate, gland-dotted.
1–9.
3–6.
(3–)4–5(–15) mm, glabrate;
pappi of 2 lanceolate scales 2–3.5 mm plus 0–4 obtuse scales 0.5–1 mm.
3–4 mm, glabrate;
pappi of 2 aristate scales 1.5–2 mm.
9–11 mm, 3-toothed (middle teeth long-acuminate, glabrous or hispid).
5.5–6.5 mm, 3-toothed (apices hairy).
= 34.
= 68.
Helianthus annuus
Helianthus schweinitzii
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.)
Of conservation concern.
Helianthus schweinitzii is distinguished by its relatively small heads and sessile to subsessile, narrowly lanceolate leaves with revolute margins. Chromosome number, typification issues, and identification of voucher specimens were updated by J. F. Matthews et al. (1997).
Helianthus schweinitzii is found on the Carolina piedmont. It was listed as endangered in the Federal Register on May 7, 1991, and is known from 16 populations. It is in the Center for Plant Conservation’s National Collection of Endangered Plants.
(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
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USDA Plants Database- LBJ Wildflower Center
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