Helianthus debilis |
Helianthus argophyllus |
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cucumberleaf sunflower, weak sunflower |
silverleaf sunflower |
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Habit | Annuals or perennials, 30–200 cm (taprooted). | Annuals, 100–300 cm. | ||||||||||||||||
Stems | decumbent to erect, glabrous, hirsute, or puberulent. |
(silvery white) erect, usually tomentose or floccose. |
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Leaves | mostly cauline; mostly alternate; petioles 1–7 cm; blades deltate-ovate, lance-ovate, or ovate, 2.5–14 × 1.8–13 cm, bases cordate to truncate or broadly cuneate, margins subentire to serrate, abaxial faces glabrate to hispid, not gland-dotted. |
mostly cauline; mostly alternate; petioles 2–10 cm; blades ovate to lance-ovate, 15–25 × 10–20 cm, bases truncate to subcordate, margins entire or serrulate, abaxial faces usually floccose, sericeous, or tomentose, gland-dotted. |
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Peduncles | 9–50 cm. |
2–8 cm. |
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Involucres | hemispheric, 10–22 mm diam. |
hemispheric, 20–30 mm diam. |
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Ray florets | 11–20; laminae 12–23 mm. |
15–20; laminae 20–30 mm. |
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Disc florets | 30+; corollas 4.5–5 mm, lobes usually reddish, sometimes yellow; anthers dark, appendages dark (style branches usually reddish, rarely yellow). |
150+; corollas 6.5–7.5 mm, lobes reddish; anthers dark, appendages dark (style branches reddish). |
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Phyllaries | 20–30, lanceolate, 8–17 × 1–3 mm, apices acute to long-attenuate, abaxial faces glabrous or ± hispid, not gland-dotted. |
20–35, ovate to lance-ovate, 15–18 × (2–)5–8 mm, apices long-attenuate, abaxial faces usually densely white-villous, gland-dotted. |
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Heads | 1–3. |
1–5. |
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Cypselae | 2.5–3.2 mm, glabrous or sparsely hairy; pappi of 2 lanceolate or lance-linear scales 1.2–2.5 mm. |
4–6 mm, glabrate; pappi of 2 aristate scales 2–2.7 mm. |
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Paleae | 7.5–8 mm, apices 3-toothed (middle teeth acuminate, usually glabrous or hispid, sometimes ± villous or bearded). |
10–11 mm, 3-toothed (apices glabrous or sparsely villous). |
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2n | = 34. |
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Helianthus debilis |
Helianthus argophyllus |
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Phenology | Flowering late summer–fall. | |||||||||||||||||
Habitat | Open areas, sandy soils | |||||||||||||||||
Elevation | 0–30+ m (0–100+ ft) | |||||||||||||||||
Distribution |
AL; CT; FL; GA; LA; MA; MD; MI; MS; NC; NH; NY; PA; RI; SC; TX; VA; VT; WV
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FL; NC; TX [Introduced in South America (Argentina), Africa, Australia] |
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Discussion | Subspecies 5 (5 in the flora). C. B. Heiser (1956) placed 8 subspecies in Helianthus debilis; he noted that alternative taxonomic treatments might recognize these in as many as three species, or expand the single species to include H. petiolaris. Later, Heiser et al. (1969) separated three of the subspecies as H. praecox. Isozyme data (R. P. Wain 1982, 1983; L. H. Rieseberg and M. F. Doyle 1989) show that all are closely related. Documented hybridization with H. annuus further complicates the situation. The treatment by Heiser et al. is followed here. Helianthus debilis is adventive beyond the Atlantic and Gulf coasts of the United States. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Helianthus argophyllus hybridizes naturally with H. annuus. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 21, p. 150. | FNA vol. 21, p. 149. | ||||||||||||||||
Parent taxa | Asteraceae > tribe Heliantheae > subtribe Helianthinae > Helianthus | Asteraceae > tribe Heliantheae > subtribe Helianthinae > Helianthus | ||||||||||||||||
Sibling taxa | ||||||||||||||||||
Subordinate taxa | ||||||||||||||||||
Name authority | Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 367. (1841) | Torrey & A. Gray: Fl. N. Amer. 2: 318. (1842) | ||||||||||||||||
Web links |