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POLYGONACEAE BUCKWHEAT FAMILY

Mihai Costea & James L. Reveal, family description, key to genera; treatment of genera revised in consultation with James L. Reveal, except as noted

Annual to shrub [tree]. Stem: nodes swollen or not. Leaf: simple, basal or cauline, generally alternate; ocreae present or 0, generally scarious, persistent or not. Inflorescence: flower clusters in axillary to terminal cyme-, panicle-, raceme-, spike-, umbel- or head-like arrangements, entire inflorescence or main inflorescence branches generally subtended by bracts ("inflorescence bracts"); peduncles present or 0; flower clusters in Eriogoneae-Eriogonoideae subtended by involucre of >= 1 free or ± fused, sometimes awn-tipped bracts ("involucre bracts") or, in Polygonoideae and rarely in Eriogonoideae, not (if bracts completely fused, involucre "tubular"); pedicels in Eriogoneae each often subtended by 2 free, transparent, linear bractlets or in Polygonoideae all subtended by 2+ fused, membranous, wide bractlets. Flower: generally bisexual, small, 1–200 per node; perianth parts 2–6, generally in 2 whorls, free or basally fused, generally petal-like, often ± concave adaxially, often darker at midvein, often turning ± red or ± brown in age; stamens [1]3 or 6–9 in 2 whorls; ovary superior, 1-chambered, ovule 1, styles 1–3. Fruit: achenes, included in or exserted from perianth, generally 3-angled, ovoid or elliptic, generally glabrous.
48 genera, ± 1200 species: worldwide, especially northern temperate; some cultivated for food (Coccoloba, sea-grape; Fagopyrum, Rheum, Rumex) or ornamental (Antigonon, lovechain; Coccoloba; Muehlenbeckia; Persicaria; Polygonum), a few timbered (Coccoloba; Triplaris). Several (Emex; Fallopia; Persicaria; Polygonum; Rumex) are weeds. [Freeman & Reveal 2005 FNANM 5:216–601] Treatment of genera in Eriogonoideae based on monographic work of James L. Reveal. Involucre number throughout is number (1–many) per ultimate grouping, at tips of ultimate branches; flower number is per flower cluster or involucre, unless otherwise stated. Fagopyrum esculentum Moench not naturalized, considered an historical waif (or garden weed ± presently), therefore not treated. —Scientific Editor: Thomas J. Rosatti.

Key to Polygonaceae

POLYGONUM KNOTWEED

Mihai Costea

Annual, perennial herb to shrub. Stem: prostrate to erect, 8–16-ribbed or 4–5-angled with ribs 0 or obscure; glabrous or papillate-scabrous. Leaf: cauline, alternate, petioled or not; ocrea generally jointed to leaf, generally cylindric proximally, generally translucent distally, white or silvery, 2-lobed, glabrous, disintegrating to fibers or completely; blade linear, lanceolate, elliptic, ovate, or subround, entire. Inflorescence: axillary, terminal, generally spike-like; peduncle 0; pedicels present or 0, included in to exserted from bractlets; flowers 1–7(10). Flower: bisexual, base not stalk-like; perianth not enlarging, bell- to urn-shaped, glabrous, white or green-white to pink; perianth parts 5, fused 3–60[70]%, petal- or sepal-like, similar [or not], outer ± keeled or not, < to > inner, midveins generally a different shade or color than rest of perianth; stamens 3–8 (some staminodes or not), filaments or at least innermost free, wider at base, fused to perianth tube or not, anthers elliptic to oblong, white-yellow or generally pink to purple (orange-pink); styles (2)3, generally spreading, free or fused basally, stigmas 2–3, head-like. Fruit: included or exserted, wings 0, angles (2)3, 1 face much narrower than other (1)2 or not; tip beak-like, yellow-green, brown, or black. Seed: embryo curved.
± 65 species: ± worldwide; sect. Duravia restricted to western North America. (Greek: many, knee joint or seed, of uncertain meaning) [Costea 2005 Brittonia 57:1–27] Many species of sect. Polygonum with 2 kinds of fruit, differing in germination and morphology (summer fruit brown, ovate, tubercled to smooth; late-season fruit olive-green, lanceolate, smooth, 2–5 × > summer), but of little taxonomic importance. Mature, early-season plants with leaves, flowers, fruits needed for identification. Flowers "closed" or "1/2-open" should be determined on herbarium specimens. Other taxa in TJM (1993) moved to Aconogonon, Bistorta, Fallopia, Persicaria.
Unabridged etymology: (Greek: poly, many, gony, knee joint, or gone, seed, of uncertain meaning)

Key to Polygonum

P. aviculare L. KNOTWEED, KNOTGRASS
NATURALIZED
Annual. Stem: prostrate to erect, 5–200 cm, glabrous, green, ribbed, branched. Leaf: distal > distal flowers; ocreae 3–15 mm, distally disintegrating to fibers or ± completely persistent; petiole 0.3–9 mm; blade 6–50(60) mm, 0.5–22 mm wide, narrowly elliptic, lanceolate, elliptic, or obovate, green to gray-green, margin flat, tip acute or rounded. Inflorescence: axillary; flowers 1–6(8), crowded distally or not; pedicels included to exserted, 1.5–5 mm. Flower: closed or half-open; perianth 1.8–5.5 mm, generally not pouched at base, ± green, margin white to red, tube 20–57% of length, lobes overlapped or not, not keeled, oblong to obovate, tip rounded, generally hood-shaped, midvein branched or not; stamens 5–8. Fruit: included or exserted, 1.2–4.2 mm, ovate, light- to dark-brown, dull, (2)3–angled, faces ± unequal, generally coarsely striate-tubercled; late-season common or not, 2–5 mm.
2n=40,60. Taxonomically controversial, generally self-pollinated, self-fertilized, polyploid complex in which varieties to species have been named, but intergradation precludes recognition as species. [Online Interchange]

P. aviculare subsp. rurivagum (Boreau) Berher
WAIF
Annual. Stem: 1–10, prostrate to ascending, 10–40 cm, branches at most nodes, proximal widely spreading. Leaf: stem leaves 1.2–2.4 × > branch leaves; ocreae (6)8–12 mm, each proximally cylindric, distally with obvious veins, soon disintegrating to fibers; petiole 0.3–2 mm; blade narrowly elliptic to lance-linear, (10)15–27(30) mm, 0.5–4.8(8) mm wide, (4.5)5–15(19) × as long as wide, tip acute, lateral veins raised adaxially. Inflorescence: flowers 1–3; pedicels included or exserted, 1.5–3 mm. Flower: perianth 2.2–3.1 mm, green, margins pink to red, tube 26–40(42)% of length, lobes often not overlapped, oblong, ± hood-shaped; veins branched, thickened to strongly so. Fruit: generally exserted, 2.1–2.6(3) mm, ovate, black-brown, 3-angled, faces sub- or unequal, tip straight, coarsely striate-tubercled; late-season uncommon, 2.5–4 mm.
2n=60. Disturbed places; < 1000 m. California; scattered in North America, native to Europe. Jun–Nov [Online Interchange]

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Citation for the whole project: Jepson Flora Project (eds.) 2013. Jepson eFlora, http://ucjeps.berkeley.edu/IJM.html, accessed on Nov 23 2014
Citation for this treatment: [Author of taxon treatment] 2013. Polygonum, in Jepson Flora Project (eds.) Jepson eFlora, http://ucjeps.berkeley.edu/cgi-bin/get_IJM.pl?tid=80991, accessed on Nov 23 2014

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Geographic subdivisions indicated for the distribution of Polygonum aviculare subsp. rurivagum Markers link to CCH specimen records. If the markers are obscured, reload the page [or change window size and reload]. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).

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Data provided by the participants of the Consortium of California Herbaria.
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa.
Blue line denotes eFlora flowering time.