Eriogonum rotundifolium |
Polygonaceae subfam. eriogonoideae |
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round-leaf wild buckwheat, roundleaf buckwheat |
wild buckwheat |
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Habit | Herbs, spreading, annual, 0.5–4 dm, glabrous and often glaucous, greenish to grayish. | Shrubs, subshrubs, or herbs, sometimes nearly arborescent (Eriogonum), perennial, biennial, or annual, homophyllous, polycarpic (rarely monocarpic in Eriogonum); taproot solid or, rarely, chambered (Eriogonum), slender to stout. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Stems | caudex absent; aerial flowering stems erect, solid, not fistulose, 0.1–0.5(–0.7) dm, glabrous. |
prostrate or decumbent to spreading or erect, sometimes scapose, rarely absent (Eriogonum), without recurved spines, glabrous or pubescent, sometimes glandular; nodes not swollen; tendrils absent; caudex stems tightly compact to spreading and at or just below the soil surface or spreading to erect and above the soil surface, woody; aerial flowering stems decumbent to spreading or erect, arising at nodes of caudex branches, at distal nodes of aerial branches, or directly from the root, slender to stout and solid or slightly to distinctly fistulose, rarely disarticulating in ringlike segments (Eriogonum). |
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Leaves | basal; petiole 1.5–4 cm, floccose; blade cordate to orbiculate, 1–2(–3) × 1–2.5(–3) cm, densely white-tomentose abaxially, floccose or subglabrous and greenish adaxially, margins plane. |
deciduous (persistent in some shrubby and matted Eriogonum species), basal or basal and cauline, rarely only cauline, rosulate, alternate, or infrequently opposite (Goodmania) or in whorls of 3 (Gilmania); stipules absent (possibly vestigial in some perennial species of Chorizanthe); petiole present, sometimes indistinct, not articulate or with extrafloral nectaries; blade simple, rarely lobed (Pterostegia), rarely awn-tipped (Goodmania). |
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Inflorescences | cymose, open to diffuse, usually flat-topped, 5–35 × 5–35 cm; branches glabrous; bracts 3, scalelike, 1–2.5 × 0.5–2 mm. |
terminal or terminal and axillary, cymose and dichotomously or trichotomously branched, or racemose, simple or compound umbellate, or capitate; bracts usually connate proximally, leaflike or scalelike, entire apically, sometimes awn-tipped, glabrous or pubescent. |
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Peduncles | erect, straight, stoutish, 0.3–1.5 cm, glabrous. |
absent or erect to deflexed relative to inflorescence branch, sometimes reflexed, straight or curved. |
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Involucres | turbinate to campanulate, 1–2 × 1.5–2.5 mm, glabrous; teeth 5, erect, 0.4–0.8 mm. |
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Flowers | 1–2.5 mm; perianth white to pink with greenish to reddish midribs, becoming rose to red, glabrous; tepals dimorphic, those of outer whorl flabellate, those of inner whorl lanceolate; stamens included, 1.2–1.7 mm; filaments pilose proximally. |
(1–)2–30(–100) per involucral structure, occasionally with stipelike base distal to articulations (Eriogonum); perianth accrescent in fruit, mostly white to red, yellow, light green, greenish white, maroon, or purple, urceolate to campanulate, occasionally glandular or pustulose abaxially, nearly always minutely glandular along midvein adaxially, glabrous or pubescent; tepals (5–)6, in 2 whorls of 3, connate proximally, typically not forming tube (except Chorizanthe, Lastarriaea, Mucronea, Pterostegia), petaloid or, rarely, coriaceous (Lastarriaea), monomorphic or dimorphic, entire, emarginate, or lobed to laciniate apically, rarely awn-tipped (Lastarriaea) or apiculate (Eriogonum); nectary a disk at base of ovary; stamens 3, 6, or 9 (variously 3–9 in Chorizanthe, Mucronea); staminodes absent; filaments usually distinct, occasionally forming staminal tube (Chorizanthe); pistils 3-carpellate, homostylous; ovary 1-locular; ovule 1, orthotropous, placentation basal; styles 3, distinct; stigmas capitate. |
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Achenes | dark brown, 3-gonous, 1.5–2 mm, glabrous. |
brown to black or maroon, homocarpic, winged or unwinged, 3-gonous, less often lenticular or globose-lenticular to globose. |
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Seeds | embryo straight or curved. |
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Involucral | structures tubular (involucre) or consisting of a series of individual bractlike lobes (involucral bracts) arranged in whorls or spirals, rarely absent (Gilmania), awns present or absent; involucre cylindric, prismatic, turbinate, campanulate, urceolate, or funnelform with 3–8(–36) usually erect teeth or 4–12 spreading to reflexed lobes (teeth and lobes are distal portions of proximally connate involucral bracts); involucral bracts in 1–3 whorls, rarely in spirals (Johanneshowellia), free or connate only at base, linear to oblanceolate or ovate. |
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2n | = 40. |
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Eriogonum rotundifolium |
Polygonaceae subfam. eriogonoideae |
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Phenology | Flowering May–Oct. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Habitat | Sandy to gravelly flats and slopes, mixed grassland, saltbush, creosote bush, and mesquite communities, juniper woodlands | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Elevation | 600-1800 m (2000-5900 ft) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Distribution |
AZ; NM; TX; Mexico (Chihuahua, Coahuila)
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Mainly temperate regions of w North America (Alaska to Mexico); uncommon in South America (Argentina and Chile) and e North America (WVa s to c Fla, e to Mo, Okla, and Tex) |
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Discussion | Eriogonum rotundifolium is the southern counterpart to E. cernuum, being common to abundant and occasionally even weedy. Its overall range, however, is significantly smaller. It occurs in Arizona only in Cochise County, but is found more widely in New Mexico, and is common in the trans-Pecos region of western Texas, with scattered populations in Dimmit, Ector, Foard, and Knox counties outside that region. A sterile Edwin James specimen gathered in 1820 (NY) supposedly was collected near the Rocky Mountains and may be Eriogonum rotundifolium. Also seen at NY is an unattributed, redistributed collection of this species labeled only “Colorado.” Until better documented material from that state is seen, the species is considered not to be a member of the Colorado flora. F. A. Elmore (1943) reported that the round-leaf wild buckwheat was used by the Navajo (Diné) people as an emetic. My own consumption of a few seeds, as a self-experiment, produced no particular urge to vomit. Inasmuch as the treatment was taken after swallowing ants, it is difficult to know whether the ants or the seeds were the emetic. G. M. Hocking (1956) reported that the leaves were used for sore throats and the stems were eaten raw (the latter proving in the same self-experiment not to be particularly tasty, leaving a slightly sour aftertaste). Hocking also reported that the roots were used medicinally but mentioned no specific ailment. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Genera 20, species ca. 325 (19 genera, 281 species in the flora). Detailed habitat, elevation, and distribution data for the eriogonoid genera are maintained by the author and available on the Web at: “Eriogonoideae (Polygonaceae) of North America north of Mexico” (http://www.life.umd.edu/emeritus/reveal/pbio/eriog/key.html). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 5, p. 402. | FNA vol. 5, p. 218. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Parent taxa | Polygonaceae > subfam. Eriogonoideae > Eriogonum > subg. Ganysma | Polygonaceae | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Sibling taxa | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Synonyms | E. cernuum subsp. glaucescens, E. cernuum subsp. rotundifolium, E. rotundifolium var. angustius | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Name authority | Bentham: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 14: 21. (1856) | Arnott: in M. Napier, Encycl. Brit. ed. 7, 5: 126. (1832) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Web links |