Parthenium confertum |
Asteraceae tribe Heliantheae subtribe Ambrosiinae |
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gray feverfew, Gray's feverfew |
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Habit | Biennials (sometimes flowering first year or persisting), 10–30(–60+) cm. | Annuals, biennials, perennials, subshrubs, or shrubs (usually taprooted, perennating bases sometimes woody, sometimes rhizomes), mostly 3–150(–400+) cm. | ||||||||||||||||||||||||||||||||||||||||
Leaves | blades ovate or rounded-deltate to elliptic, 30–80(–120+) × 10–20(–40+) mm, usually ± pinnately or sub-bipinnately lobed, ultimate margins entire, faces strigillose, usually also with erect hairs 1–2 mm and gland-dotted. |
usually cauline, sometimes basal or basal and cauline; mostly opposite (distal sometimes alternate); petiolate or sessile; blades (palmately or pinnately nerved) deltate to linear or filiform (and intermediate shapes) sometimes 1–3+-pinnately or -ternately lobed, ultimate margins entire or toothed, faces usually hairy (scabrellous, hispidulous to sericeous, strigillose, or tomentose) and/or stipitate-glandular, or glabrous, often gland-dotted. |
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Peduncles | 2–8(–12+) mm. |
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Involucres | campanulate, cup-shaped, cylindric, hemispheric, obconic, rotate, saucer-shaped, turbinate, or urceolate (in pistillate heads, sometimes forming ± ovoid to fusiform, often ± spiny or winged burs). |
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Receptacles | usually flat to convex, sometimes conic to columnar or hemispheric, usually paleate (at least staminate heads; paleae usually spatulate to filiform, sometimes setiform, often gland-dotted; tips sometimes dilated and strigillose or ciliate; sometimes paleae 0). |
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Ray florets | 0 or 5(–8), pistillate, fertile; corollas whitish to yellowish, laminae seldom conspicuous. |
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Pistillate florets | 5; corolla laminae 0 or ± coroniform, 0.1–0.5 mm. |
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Peripheral (pistillate) florets | 0 or 1–10+; corollas (sometimes 0) usually ochroleucous or whitish, sometimes yellowish or pinkish, tubular to ± filiform (styles: stigmatic papillae in 2 lines, appendages essentially none). |
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Disc florets | 20–30+. |
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Phyllaries | outer 5 lance-ovate to elliptic, 2.5–3+ mm, inner 5 ± orbiculate, 3–3.5 mm. |
persistent or falling, mostly (3–)5–80+ in 1–8(–12+) series, distinct or connate, ovate or lance-ovate to linear, unequal to subequal, outer mostly herbaceous, inner membranous to scarious (sometimes indurate in fruit, accrescent and ultimately ovate to elliptic in Dicoria). |
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Calyculi | 0. |
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Heads | disciform or obscurely radiate, borne in open, ± paniculiform arrays. |
usually disciform, sometimes discoid (then usually unisexual) or radiate (Parthenium, laminae minute in Parthenice), borne singly or in (usually ebracteate, sometimes bracteate) corymbiform, glomerate, paniculiform, racemiform, or spiciform arrays. |
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Cypselae | ± obovoid, 2–3 mm; pappus-like enations 2, ± erect, deltate to ovate, 0.5–1 mm (sometimes a third, subulate spur near apex adaxially). |
(sometimes shed within burlike or nutlike, spiny or winged perygynia, or shed with accessory structures) fusiform, obovoid, prismatic, or pyriform, sometimes obcompressed and plumply biconvex, sometimes flattened and cucullate (lengths usually 1–2+ times diams., sometimes finely striate or 1–5-nerved, corky-winged in Dicoria and winged margins ± toothed), usually smooth, sometimes ± tuberculate or warty, glabrous or hispidulous, scabrellous, strigillose, or villous and/or gland-dotted; pappi 0 (cypselae sometimes with apical tufts of hairs, or seeming pappi actually enations from ovary walls). |
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Disc | (functionally staminate) florets 5–60+; corollas mostly ochroleucous or whitish, sometimes yellowish or pinkish (usually hairy and/or gland-dotted or stipitate-glandular), tubes shorter than to longer than cylindric or campanulate to funnelform throats, lobes 5, ± deltate; (staminal filaments usually connate, anthers usually distinct, ± connate in Parthenice and Parthenium) anther thecae usually pale; stigmatic papillae 0. |
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2n | = 36, 68, 72. |
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Parthenium confertum |
Asteraceae tribe Heliantheae subtribe Ambrosiinae |
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Phenology | Flowering Mar–Oct. | |||||||||||||||||||||||||||||||||||||||||
Habitat | Sandy plains, openings in mesquite grasslands | |||||||||||||||||||||||||||||||||||||||||
Elevation | 20–2000 m (100–6600 ft) | |||||||||||||||||||||||||||||||||||||||||
Distribution |
AZ; NM; TX; Mexico
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Mostly subtropical and warm-temperate New World |
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Discussion | Genera 12, species 76 (11 genera, 45 species in the flora). In most genera of Ambrosiinae, proximal heads are erect and pistillate and distal heads are pendulous and functionally staminate. In functionally staminate florets, the staminal filaments are usually connate and the anthers are distinct or weakly coherent. Unlike nearly all other composites, such plants are wind-pollinated. Wind-borne pollen from some members of Ambrosiinae (especially ragweeds) are sources of “hay-fever” for some people. H. Robinson (1981) affirmed inclusion of Parthenice and Parthenium in Ambrosiinae and suggested connections between Ambrosiinae and Clibadiinae and/or Ecliptinae. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 21, p. 22. | FNA vol. 21, p. 8. | ||||||||||||||||||||||||||||||||||||||||
Parent taxa | Asteraceae > tribe Heliantheae > subtribe Ambrosiinae > Parthenium | Asteraceae > tribe Heliantheae | ||||||||||||||||||||||||||||||||||||||||
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Synonyms | P. confertum var. divaricatum, P. confertum var. lyratum, P. confertum var. microcephalum | subtribe Ambrosieae, subtribe Iveae | ||||||||||||||||||||||||||||||||||||||||
Name authority | A. Gray: Proc. Amer. Acad. Arts 17: 216. (1882) | Lessing: Linnaea 5: 151. (1830) | ||||||||||||||||||||||||||||||||||||||||
Web links |