Helenium microcephalum |
Helenium microcephalum var. oöclinium |
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littlehead tarweed, smallhead sneezeweed |
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Habit | Annuals, 25–120 cm. | Plants 25–80 cm. | ||||
Stems | 1(2–10), branched distally, moderately to strongly winged, glabrous or sparsely hairy. |
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Leaves | glabrous or sparsely to moderately hairy (basal withered by flowering); proximal and mid blades narrowly elliptic to narrowly oblong-elliptic, usually serrate to undulate-serrate, sometimes deeply toothed or laciniate; distal blades narrowly elliptic to narrowly oblong-elliptic, serrate to undulate-serrate. |
proximal and mid blades serrate to undulate-serrate to occasionally deeply toothed or laciniate, glabrate; distal blades glabrous or sparsely to moderately hairy. |
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Peduncles | 1.8–8 cm, moderately hairy. |
1.5–8 cm, usually projecting terminal heads well beyond foliage. |
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Involucres | globoid to usually ovoid, 4–12 × 4–12 mm. |
8–12 × 8–12 mm. |
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Ray florets | 7–13, pistillate, fertile; corollas usually yellow throughout, sometimes reddish proximally and yellow distally, 2.6–9.1 × 1.5–6.7 mm. |
9–13; corollas usually yellow throughout, sometimes reddish proximally and yellow distally, 2.7–9.1 × 1.5–6.7 mm. |
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Disc florets | 120–400+; corollas yellow to yellow-green proximally, brown to reddish brown distally, 1.2–2.4 mm, lobes (4–)5. |
200–400+; corollas 1.7–2.4 mm, lobes 5. |
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Phyllaries | (connate proximally) moderately hairy. |
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Heads | 20–300+ per plant, in paniculiform arrays. |
20–100+ per plant. |
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Cypselae | 0.7–1.4 mm, moderately hairy; pappi of usually 6 entire, non-aristate scales (0.2–)0.3–0.7 mm. |
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Pappi | 0.4–0.7 mm. |
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2n | = 26. |
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Helenium microcephalum |
Helenium microcephalum var. oöclinium |
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Phenology | Flowering (Mar–)Apr–Jun(–Dec). | |||||
Habitat | Sandy or clay soils, ditches, washes, around ponds and lakes, along streams | |||||
Elevation | 500–1900 m (1600–6200 ft) | |||||
Distribution |
AZ; NM; OK; TX; n Mexico
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TX; Mexico (Coahuila, Nuevo León, Durango, San Luis Potosí) |
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Discussion | Varieties 2 (2 in the flora). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 21, p. 433. | FNA vol. 21, p. 434. | ||||
Parent taxa | ||||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | H. oöclinium | |||||
Name authority | de Candolle: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 5: 667. (1836) | (A. Gray) Bierner: Sida 5: 47. (1972) | ||||
Web links |