Belongs within: Polygonaceae.
Contains: Polygonum sect. Persicaria, Polygonum sect. Aconogonon, Polygonum sect. Bistorta.
Polygonum, the knotweeds, is a cosmopolitan genus of herbs, shrubs and vines most diverse in northern temperate regions. Leaves are generally petioled and between 5 to 35 cm long in members of the subgenus Persicaria whereas they are more or less sessile and less than five centimetres long in species of the subgenus Polygonum (Hickman 1993).
Characters (from Hickman 1993): Annual, perennial, shrub or 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 with 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.
<==Polygonum Linnaeus 1753A61
|--P. subg. PolygonumH93
| | i. s.: P. bolanderiH93
| | P. paronychiaH93
| | P. shastenseH93
| |--P. sect. PolygonumH93
| | |--P. arenastrum [incl. P. montereyense]H93
| | |--P. argyrocoleonH93
| | |--P. aviculareH93
| | |--P. marinenseH93
| | |--P. patulumH93
| | |--P. prolificumH93
| | |--P. ramosissimumH93
| | `--P. robertiiH93
| |--P. sect. DuraviaH93
| | |--P. bidwelliaeH93
| | |--P. californicumH93
| | `--P. parryiH93
| `--P. sect. MonticolaH93
| |--P. douglasiiH93
| | |--P. d. ssp. douglasii [incl. P. douglasii var. latifolium]H93
| | |--P. d. ssp. austiniaeH93
| | |--P. d. ssp. johnstonii [incl. P. sawatchense]H93
| | |--P. d. ssp. majusH93
| | `--P. d. ssp. spergulariiformeH93
| |--P. minimumH93
| `--P. polygaloidesH93
| |--P. p. ssp. polygaloidesH93
| |--P. p. ssp. confertiflorumH93
| |--P. p. ssp. esotericumH93
| `--P. p. ssp. kelloggiiH93
`--P. subg. PersicariaH93
| i. s.: P. barbatum Linnaeus 1753H78 [=Persicaria barbataLK14]
| ‘Persicaria’ bistortaV09
| P. chinense Linnaeus 1753H78 [=Persicaria chinensisD07]
| P. glabrumVB02 [=Persicaria glabraK10]
| ‘Persicaria’ glacialisO88
| P. nepalense Meissn. 1826H78 (see below for synonymy)
| ‘Persicaria’ odorataH90
|--P. sect. PersicariaH93
|--P. sect. AconogononH93
|--P. sect. BistortaH93
`--P. (sect. Cephalophilon) capitatumH93 [=Persicaria capitataH90]
Polygonum incertae sedis:
P. acuminatumH70
P. benguetense Merr. 1915H78
P. chilenseD03
P. cumingianum [incl. P. celebicum]H78
P. dumetorumC55
P. emarginatumC55
P. fagopyrumC55
P. longisetum DeBr. in Miq. 1854H78
P. maritimumC55
P. minus Huds. 1762H78
P. paniculatum [incl. P. polyanthos]H78
P. perfoliatum Linnaeus 1762H78
P. plebeium [incl. P. aviculare var. dryandri]C06
|--P. p. var. plebeiumPP07
`--P. p. var. indicaPP07
P. pubescensH78
P. runcinatum Don 1825H78
P. salicifoliumBG96
P. senegalenseGC05
P. serrulatumA27
P. sieboldiF92
P. tataricumC55
P. thunbergiF92
P. viviparumCS77
Polygonum nepalense Meissn. 1826H78 [=Persicaria nepalensisO88; incl. P. alatum Buch.-Ham. ex Spreng. 1827H78, P. microcephalum var. papuanum Warb. 1893H78]
*Type species of generic name indicated
References
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[D03] Dusén, P. 1903. The vegetation of western Patagonia. In: Scott, W. B. (ed.) Reports of the Princeton University Expeditions to Patagonia, 1896–1899 vol. 8. Botany pp. 1–34. The University: Princeton (New Jersey).
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[H90] Harden, G. J. (ed.) 1990. Flora of New South Wales vol. 1. New South Wales University Press.
[H78] Henty, E. E. 1978. Polygonaceae. In: Womersley, J. S. (ed.) Handbooks of the Flora of Papua New Guinea vol. 1 pp. 222–248. Melbourne University Press: Carlton South (Australia).
[H93] Hickman, J. C. (ed.) 1993. The Jepson Manual: Higher Plants of California. University of California Press: Berkeley (California).
[K10] Keighery, G. 2010. The naturalised vascular plants of the Pilbara region, Western Australia. Records of the Western Australian Museum Supplement 78 (1): 299–311.
[LK14] Lyons, M. N., G. J. Keighery, L. A. Gibson & T. Handasyde. 2014. Flora and vegetation communities of selected islands off the Kimberley coast of Western Australia. Records of the Western Australian Museum Supplement 81: 205–244.
[O88] Ohba, H. 1988. The alpine flora of the Nepal Himalayas: an introductory note. In: Ohba, H., & S. B. Malla (eds) The Himalayan Plants vol. 1. The University Museum, University of Tokyo, Bulletin 31: 19–46.
[PP07] Pandey, R. P., & P. M. Padhye. 2007. Studies on phytodiversity of Arid Machia Safari Park-Kailana in Jodhpur (Rajasthan). Bulletin of the Botanical Survey of India 49: 15–78.
[V09] Verdcourt, B. (ed.) 2009. Additions to the wild fauna and flora of the Royal Botanic Gardens, Kew. XXVI. Miscellaneous records. Kew Bulletin 64 (1): 183–194.
[VB02] Vijay, S. K., & T. N. Bhardwaja. 2002. Vegetation and phenodynamics of wetlands of central Rajasthan. Journal of the Bombay Natural History Society 99 (3): 573–581.