Polygonaceae subfam. Eriogonoideae

Arnott in M. Napier

in M. Napier, Encycl. Brit. ed. 7, 5: 126. 1832

Common names: Wild Buckwheat
Treatment appears in FNA Volume 5. Treatment on page 218. Mentioned on page 216, 217, 222, 322, 441, 475, 476.
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 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). Leaves 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). Inflorescences 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. Peduncles absent or erect to deflexed relative to inflorescence branch, sometimes reflexed, straight or curved. 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. Flowers (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. Achenes brown to black or maroon, homocarpic, winged or unwinged, 3-gonous, less often lenticular or globose-lenticular to globose. Seeds: embryo straight or curved.

Distribution

Mainly temperate regions of w North America (Alaska to Mexico), uncommon in South America (Argentina and Chile) and e North America (W.Va. s to c Fla., e to Mo., Okla., and Tex.).

Discussion

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).

Key

1 Plants annual with involucre forming distinct tube, this cylindric or prismatic and awn-tipped typically with at least some awns uncinate or curved, rarely turbinate or urceolate to campanulate and then with 5 divergent, straight awns, or reduced to 1-4, often awn-tipped involucral bracts; flowers mostly 1-2(-6) per involucre > 2
1 Plants perennial or biennial, or, if annual, with involucre forming distinct tube, this turbinate to campanulate or hemispheric and awnless or tipped with erect, straight awns or reduced to awnless involucral bracts, absent entirely in Gilmania; flowers mostly (2-)6-200 per involucre (Eriogoneae, Eriogonineae) > 10
2 Involucres reduced to 1 highly modified, 2-winged bract; leaf blades entire or variously lobed; stems sprawling and spreading (Pterostegieae) Pterostegia
2 Involucres tubular or reduced to 3(-4) bracts; leaf blades entire; stems erect to prostrate > 3
3 Involucres reduced to 3(-4) bracts; tepals mucronate or awn-tipped; California > 4
3 Involucres tubular; tepals not mucronate or awn-tipped (Chorizanthineae); widespread > 5
4 Perianths yellowish, densely tomentose abaxially; tepals mucronate apically; stamens 6 or 9; inflorescence branches tomentose (Hollisteriineae) Hollisteria
4 Perianths light green to greenish white, thinly pubescent abaxially; tepals acute or awn-tipped apically; stamens 3; inflorescence branches thinly pubescent (Chorizanthineae) Lastarriaea
5 Inflorescence bracts opposite, mostly 2, sometimes numerous and whorled; flowers 1(-2) per involucre; w North America Chorizanthe
5 Inflorescence bracts alternate and positioned on one side of branch or perfoliate around branch, 3-lobed or parted; flowers (1-)2-6 per involucre; widespread > 6
6 Involucres 5-toothed, each terminated by divergent awn; flowers 4(-6) per involucre; perianth pubescent abaxially; wc California Aristocapsa
6 Involucres 2-4(6)-lobed or -toothed, or, if 5-awned apically, involucre with additional basal awns; flowers (1-)2-3 per involucre, perianth glabrous by densely papillate or pubescent abaxially; California > 7
7 Involucres not awned basally; California > 8
7 Involucres awned basally; sw North America > 9
8 Perianths pubescent abaxially; flowers bisexual Mucronea
8 Perianths glabrous, densely papillate abaxially; flowers bisexual and unisexual, with proximal 1 pistillate and distal 1 bisexual Systenotheca
9 Basal awns 3, on saccate lobes; terminal awns 5, straight, involucres 3-angled; flowers 2 per involucre; sw North America Centrostegia
9 Basal awns 6, on nonsaccate basal lobes; terminal awns 6, uncinate; involucres 6-angled; flowers 3 per involucre; sw California Dodecahema
10 Plants perennial, if annual or biennial involucre tubular and awnless > 11
10 Plants annual; involucres tubular and awn-tipped or series of free or basally connate, awnless bracts, rarely absent (Gilmania) > 12
11 Involucres tubular, the lobes rarely connate proximally; plants annual, biennial, or perennial; widespread Eriogonum
11 Involucres reduced to series of 2-5 obscure, awnless bracts; plants perennial shrubs; ec California Dedeckera
12 Involucres not awned or absent > 13
12 Involucres awn-tipped > 16
13 Involucral bracts in 2 whorls of 3; sw Wyoming to ne Arizona and nw New Mexico Stenogonum
13 Involucral bracts absent or in 1 whorl or tight spiral; California, Nevada, sw Utah > 14
14 Stamens 3; s California, sw Arizona Nemacaulis
14 Stamens 9; se California, s Nevada, sw Utah > 15
15 Perianths thinly pubescent abaxially; involucral bracts absent; Death Valley, California Gilmania
15 Perianths glabrous, smooth or minutely pustulose; involucral bracts (3-)4(-7); se California, s Nevada, sw Utah Johanneshowellia
16 Involucres not tubular; se California, ec Nevada Goodmania
16 Involucres tubular; widespread. [17. Shifted to left margin.—Ed.] > 17
17 Involucral awns 5(-6); tepals 3-lobed or laciniate apically; achenes 3-gonous; s California Sidotheca
17 Involucral awns either (3-)4 or 7-36; tepals mostly entire, rarely irregularly divided or retuse apically; achenes globose-lenticular; widespread > 18
18 Involucral awns (3-)4; leaf blades linear to spatulate, margins entire; se Washington e to sw Wyoming and s to Mexico Oxytheca
18 Involucral awns 7 or more, rarely 4; leaf blades broadly obovate or spatulate to oblong or oblanceolate, margins ciliate-denticulate; s California Acanthoscyphus