Description: Annual or perennial herbs, shrubs or climbers; stems often with swollen nodes, the nodes surrounded by a membranous or scarious sheath (ocrea), usually shortly tubular, often disintegrating [or reduced or rarely absent].
Leaves alternate, opposite or whorled, simple and usually entire, petiolate or sessile, sometimes articulate; sunken (pit) nectaries sometimes present at base of petiole on lower surface.
Inflorescence a raceme or spike-like panicle; flowers clustered or solitary, each cluster subtended by an ocreola and each flower by a similar small persistent sheath. Flowers actinomorphic, bisexual or unisexual (plants dioecious or monoecious); pedicels mostly articulate, with portion ('fruiting pedicel') falling with fruit. Perianth segments mostly 4–6 in 2 whorls, imbricate, united at least at base, sepaloid and greenish or petaloid and white to deep pink, persistent, often enlarged in fruit and membranous, hard or succulent. Stamens mostly 2–9; anthers versatile or basifixed, 2-locular, longitudinally dehiscent. Ovary superior, 1-locular with a solitary basal ovule; styles 1–4, free or fused at base; stigmas variable.
Fruit an achene, trigonous or lenticular, mostly enclosed by persistent perianth and falling as a unit with portion of pedicel.
Distribution and occurrence: World: 40 gen., 800 spp., cosmop., especially in N temp. regions. Aust.: 10 gen. (4 gen. native), 57 spp., all States.
Angiosperm Phylogeny Website (Family: Polygonaceae, Order: Caryophyllales)
Various species are cultivated as ornamentals or food crops, including Antigonon leptopus Hook. & Arn. (Coral Vine), Fagopyrum esculentum Moench (Buckwheat), Muehlenbeckia platyclada (Homalocladium platycladum), Persicaria odorata (Lour.) Sojak (Vietnamese Mint), Persicaria orientalis (L.) Spach (Princes Feathers), Rheum x rhabarbarum L. (Rhubarb). Various species are weedy, especially introduced species of Acetosa, Acetosella (Sorrel), Emex and Rumex (Docks).
Text by K. L. Wilson
| ||Key to the genera|| |
|1||Perianth segments 4 or 5; anthers versatile||2|
|Perianth segments 6 (occasionally 5 in male Emex flowers); anthers basifixed||8|
|2||Ocreas entire, tubular, often only shortly so and soon disintegrating, pale brown, upper margin often ciliate or with a green limb; stamen filaments subulate or filiform||3|
|Ocreas lacerate, often nearly to base, glabrous, silvery or white; stamen filaments subulate above, widely dilated in lower half|
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|3||Shrubs with thorn-like branch tips; extrafloral nectaries absent||Duma|
|Vines or shrubs without thorn-like branch tips; extrafloral nectaries present or absent|
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|4||Flowers mostly unisexual; stigmas elongate or peltate, fimbriate; extrafloral nectary present at base of petiole on abaxial surface||5|
|Flowers bisexual; stigmas capitate, usually smooth; petiolar nectaries absent or present|
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|5||Outer 3 perianth segments winged in fruit; stigmas shortly elongate; rhizomatous perennials with stout erect annual stems||Reynoutria|
|Perianth segments not winged but often enlarged in fruit, and becoming fleshy or membranous; stigmas peltate; slender perennial shrubs or woody herbs or climbers, not rhizomatous|
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|6||Nut much exceeding perianth segments||Fagopyrum|
|Nut enclosed by perianth segments|
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|7||Outer 3 perianth segments winged or keeled in fruit; twining or decumbent, slender but woody herbs; nectary present at base of petiole||Fallopia|
|Perianth segments not winged or keeled; erect to procumbent non-woody herbs, slender to stout; nectaries absent|
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|8||Outer 3 perianth segments in female flowers enlarged and hardened in fruit and produced in a rigid spreading spine; perianth segments subequal in male flowers||Emex|
|Outer 3 perianth segments smaller than inner 3, not spiny or hardened|
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|9||Flowers unisexual; inner 3 perianth segments scarcely exceeding the nut; leaves hastate||Acetosella|
|Flowers mostly bisexual; inner 3 perianth segments much exceeding nut; leaves variable|
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|10||Leaves hastate or sagittate at base; inner 3 perianth segments membranous, inflated||Acetosa|
|Leaves rounded, cuneate or cordate at the base; inner 3 perianth segments leathery, not inflated, often toothed|
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