Parthenium confertum |
Parthenium argentatum |
|
---|---|---|
gray feverfew, Gray's feverfew |
guayule |
|
Habit | Biennials (sometimes flowering first year or persisting), 10–30(–60+) cm. | Shrubs, 30–100+ cm. |
Leaf | 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. |
blades lanceolate to oblanceolate, 15–25(–40+) × 6–15(–25+) mm, margins mostly entire, some with 1–2(–5) sharp teeth, faces densely strigillose (gray to white) and obscurely or not at all gland-dotted. |
Peduncles | 2–8(–12+) mm. |
1–2(–6+) mm. |
Pistillate florets | 5; corolla laminae 0 or ± coroniform, 0.1–0.5 mm. |
5; corolla laminae ovate, 1.2–1.5 mm. |
Disc florets | 20–30+. |
20–30+. |
Phyllaries | outer 5 lance-ovate to elliptic, 2.5–3+ mm, inner 5 ± orbiculate, 3–3.5 mm. |
outer 5 oval-elliptic, 2.5–3+ mm, inner 5 ± orbiculate, 3.5–4 mm. |
Heads | disciform or obscurely radiate, borne in open, ± paniculiform arrays. |
radiate, in glomerules of 3–5+ at ends of ± ebracteate stalks 8–15(–20+) cm. |
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). |
± obovoid, 2.5–3 mm; pappus-like enations 2(–4), erect to spreading, ± subulate, 0.3–0.8 mm. |
2n | = 36, 68, 72. |
= 36. |
Parthenium confertum |
Parthenium argentatum |
|
Phenology | Flowering Mar–Oct. | Flowering Apr–Jun. |
Habitat | Sandy plains, openings in mesquite grasslands | Calcareous soils |
Elevation | 20–2000 m (100–6600 ft) | 1000–1500 m (3300–4900 ft) |
Distribution |
AZ; NM; TX; Mexico
|
TX; Mexico
|
Discussion | Guayule has sometimes been used for commercial production of natural rubber. Hybrids between Parthenium argentatum and P. incanum have been noted. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
|
Source | FNA vol. 21, p. 22. | FNA vol. 21, p. 21. |
Parent taxa | Asteraceae > tribe Heliantheae > subtribe Ambrosiinae > Parthenium | Asteraceae > tribe Heliantheae > subtribe Ambrosiinae > Parthenium |
Sibling taxa | ||
Synonyms | P. confertum var. divaricatum, P. confertum var. lyratum, P. confertum var. microcephalum | |
Name authority | A. Gray: Proc. Amer. Acad. Arts 17: 216. (1882) | A. Gray: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 86. (1859) |
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