Helianthus debilis |
Helianthus giganteus |
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cucumberleaf sunflower, weak sunflower |
giant sunflower, hélianthe géant, tall sunflower |
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Habit | Annuals or perennials, 30–200 cm (taprooted). | Perennials, 100–400 cm (rhizomatous). | ||||||||||||||||
Stems | decumbent to erect, glabrous, hirsute, or puberulent. |
(usually reddish) erect, hairy. |
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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. |
cauline; mostly alternate; petioles 0–1.2 cm (ciliate); blades (3-nerved from bases) lanceolate to lance-ovate, 7–20 × 1.2–3.5 cm, bases cuneate, margins serrulate to subentire (± flat), abaxial faces scabrous or ± hirsute, sometimes gland-dotted. |
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Peduncles | 9–50 cm. |
8–12 mm. |
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Involucres | hemispheric, 10–22 mm diam. |
hemispheric, 10–24 mm diam. |
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Ray florets | 11–20; laminae 12–23 mm. |
12–20; laminae (often pale yellow) 15–25 mm (abaxial faces not gland-dotted). |
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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). |
60+; corollas 5–6 mm, lobes yellow; anthers dark brown or black, appendages dark. |
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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. |
20–25 (loose or spreading), linear, 8–15 × 1.2–2 mm, (margins usually ciliate) apices acute to attenuate, abaxial faces sparsely strigose, not gland-dotted. |
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Heads | 1–3. |
1–12. |
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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. |
3–4 mm, glabrate; pappi of 2 aristate scales 2.4–3 mm. |
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Paleae | 7.5–8 mm, apices 3-toothed (middle teeth acuminate, usually glabrous or hispid, sometimes ± villous or bearded). |
7–9 mm, entire or ± 3-toothed (apices acute, hairy). |
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2n | = 34. |
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Helianthus debilis |
Helianthus giganteus |
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Phenology | Flowering late summer–fall. | |||||||||||||||||
Habitat | Usually wet, open sites | |||||||||||||||||
Elevation | 10–600+ m (0–2000+ 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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CT; DC; DE; GA; IA; IL; IN; KS; KY; MA; MD; ME; MI; MN; MS; NC; NJ; NY; OH; PA; SC; TN; VA; VT; WI; WV; NB; NF; NS; ON; QC
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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 giganteus was probably introduced in Newfoundland. It intergrades with H. nuttallii and H. grosseserratus; it is distinctive in its hairy, reddish-colored stems, dark anther appendages, and prominent setae on the petioles. The natural hybrid of H. giganteus with H. grosseserratus has been called H. luxurians E. Watson (R. W. Long 1954). Hybrids of H. giganteus with H. divaricatus have been referred to as H. ambiguus (Torrey & A. Gray) Britton and H. ×divariserratus R. W. Long (Long 1954). (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. 165. | ||||||||||||||||
Parent taxa | Asteraceae > tribe Heliantheae > subtribe Helianthinae > Helianthus | Asteraceae > tribe Heliantheae > subtribe Helianthinae > Helianthus | ||||||||||||||||
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Subordinate taxa | ||||||||||||||||||
Synonyms | H. alienus, H. validus | |||||||||||||||||
Name authority | Nuttall: Trans. Amer. Philos. Soc., n. s. 7: 367. (1841) | Linnaeus: Sp. Pl. 2: 905. (1753) | ||||||||||||||||
Web links |