Helianthus hirsutus
Helianthus paradoxus
hairy sunflower
Paradox sunflower, Pecos sunflower
erect, hirsute.
erect, glabrous or ± hispid.
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).
mostly cauline; opposite (proximal) or mostly alternate;
petioles 1.5–6 cm;
blades lanceolate to lance-ovate, 7–17.5 × 1.7–8.5 cm, bases cuneate, margins entire or (larger leaves) toothed, abaxial faces ± scabrous, not gland-dotted.
1–5 cm.
12–18 cm.
hemispheric, 10–25 mm diam.
hemispheric, 15–20 mm diam.
10–15;
laminae 15–20 mm.
12–20;
laminae 20–30 mm.
40+;
corollas 5.5–6.5 mm, lobes yellow;
anthers dark brown or black, appendages dark or yellowish.
50+;
corollas 5–5.5 mm, lobes reddish;
anthers dark, appendages yellowish or dark (style branches reddish).
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.
15–25, lanceolate to lance-ovate, 6–19 × 0.7–4 mm (equaling or slightly surpassing discs), (margins ciliate) apices (spreading to recurved) acuminate, abaxial faces usually glabrate or sparsely hispid.
1–7.
1–5.
4–4.5 mm, glabrate or distally puberulent;
pappi of 2 aristate scales 2.5–3.2 mm.
3–4 mm, glabrous;
pappi of 2 lanceolate scales 2.5–2.9 mm.
7–10 mm, 3-toothed (apices yellowish, hairy).
8–9 mm, apices 3-toothed (apices glabrous).
= 68.
= 34.
Helianthus hirsutus
Helianthus paradoxus
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.)
Of conservation concern.
Helianthus paradoxus is listed by the U.S. Fish and Wildlife Service as an endangered species and is in the Center for Plant Conservation’s National Collection of Endangered Plants. It is of hybrid origin; the parents are H. annuus and H. petiolaris (L. H. Rieseberg et al. 1990). It occupies a different habitat type than either parent (H. annuus usually on clay-based mesic soils and H. petiolaris usually on dry, sandy soils).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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