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©Copyright 1993 by the Regents of the University of California

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POLYGONACEAE

BUCKWHEAT FAMILY

James C. Hickman

Annual to trees, some dioecious
Stem: nodes often swollen
Leaves simple, basal or cauline, alternate, opposite, or whorled, generally entire; stipules 0 or obvious and fused into a generally scarious sheath around stem
Inflorescence: small cluster, axillary or arrayed in cymes or panicles; involucres sometimes subtending 1–many flowers
Flower generally bisexual, small, ± radial; perianth generally 5–6-lobed, base ± tapered, often jointed to pedicel; stamens 2–9, often in 2 whorls; ovary superior, styles generally 3, generally fused at base
Fruit: achene, generally enclosed by persistent perianth, generally 3-angled, ovoid, and glabrous
Genera in family: 50 genera, 1100 species: worldwide, especially n temp; some cultivated for food (Fagopyrum ; Rheum , rhubarb; Rumex , sorrel) or ornamental (Antigonon , coral-vine; Muehlenbeckia ; Polygonum )
Reference: [Ronse Decraene & Akeroyd 1988 Bot J Linn Soc 98:321–371; Reveal et al. 1989 Phytologia 66(2–4):83–414]
Treatments of the 15 eriogonoid genera are based on the monographic work of James L. Reveal, who is gratefully acknowledged.

POLYGONUM

KNOTWEED, SMARTWEED

Annual, perennial herb, shrub, vine
Stem prostrate to erect, or climbing, or floating, < 3 m
Leaves generally cauline, alternate, sessile or petioled; stipules fused, sheathing stem above nodes, generally scarious or membranous; blade sometimes obviously jointed to stipule sheath
Inflorescence: unit a 1–8-flowered cluster, these arrayed singly or in head-like to open panicles
Flower: perianth lobes generally 5; stamens 3–8, filaments generally wider at base
Fruit generally ovoid, 3-angled, sometimes round, flat, indented; shiny to dull, brown to black
Species in genus: ± 300 species: worldwide, especially n temp
Etymology: (Greek: many knees, from swollen nodes of some species)
Reference: [Ronse Decraene & Ackeroyd 1988 Bot J Linn Soc 98:321–371]
Segregate genera (e.g., Bistorta, Fallopia, Persicaria ) are sometimes recognized.

Introduced

P. argyrocoleon Kunze

Annual
Stem erect, < 6 dm, round, ribbed
Leaf generally 2–4 cm, sessile; blades linear to lanceolate, reduced gradually upward, then abruptly at inflorescence
Inflorescence: branches raceme-like, restricted to stem tips, ± 15 cm; flowers 4–8 per axil; bracts < flowers or falling early
Flower: perianth ± 2 mm, exserted from stipule, margin red
Fruit < 2 mm, widely ovoid, 3 sides ± equal, brown, shiny
Chromosomes: 2n=40
Ecology: Fields, disturbed places
Elevation: < 1000 m.
Bioregional distribution: California (especially s)
Distribution outside California: native to sw Asia
Flowering time: Jun–Oct

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