Helianthus debilis |
Helianthus pauciflorus |
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cucumberleaf sunflower, weak sunflower |
stiff sunflower |
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Habit | Annuals or perennials, 30–200 cm (taprooted). | Perennials, 50–200 cm (rhizomatous). | ||||||||||||||||||||
Stems | decumbent to erect, glabrous, hirsute, or puberulent. |
erect, scabro-hispid. |
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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 basal; opposite, or opposite (proximal) and alternate; petioles 0–1 cm; blades lance-ovate to oblong-lanceolate, or rhombic-ovate to lance-linear, 5–27 × 2–6 cm, bases cuneate, margins serrate to subentire, abaxial faces sparsely hispid, sparsely, if at all, gland-dotted (cauline smaller). |
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Peduncles | 9–50 cm. |
3–12 cm. |
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Involucres | hemispheric, 10–22 mm diam. |
hemispheric, 15–23 mm diam. |
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Ray florets | 11–20; laminae 12–23 mm. |
10–20; laminae 20–35 mm (abaxial faces usually 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). |
75+; corollas 6.5–7 mm, lobes usually reddish, sometimes yellow; anthers dark, appendages dark (style branches yellow). |
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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. |
25–35, ovate, 6–10 × 3–5 mm, (margins ciliate) apices acute, abaxial faces glabrate to hispid. |
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Heads | 1–3. |
1–10. |
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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. |
5–6 mm, glabrate; pappi of 2 aristate scales 4.5–5 mm plus 1–4 smaller aristate scales 0.3–2 mm. |
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Paleae | 7.5–8 mm, apices 3-toothed (middle teeth acuminate, usually glabrous or hispid, sometimes ± villous or bearded). |
9–10 mm, shallowly 3-toothed to subentire (apices ciliate, hairy). |
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2n | = 102 (subspecies unknown). |
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Helianthus debilis |
Helianthus pauciflorus |
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Distribution |
AL; CT; FL; GA; LA; MA; MD; MI; MS; NC; NH; NY; PA; RI; SC; TX; VA; VT; WV
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AR; CO; CT; GA; IA; IL; IN; KS; KY; MA; ME; MI; MN; MO; MT; ND; NE; NH; NJ; NM; OK; PA; RI; SD; TX; VA; VT; WI; WY; AB; BC; MB; NB; NS; ON; PE; QC; SK
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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.) |
Subspecies 2 (2 in the flora). Variation within Helianthus pauciflorus is complex and is complicated by hybridization with H. tuberosus. Hybrids with H. tuberosus are known as H. ×laetiflorus, which is frequently cultivated. (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. 160. | ||||||||||||||||||||
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) | Nuttall: Gen. N. Amer. Pl. 2: 177. (1818) | ||||||||||||||||||||
Web links |