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2007-10-16T07:36:31Z

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{{Taxobox
| color = lightgreen
| name = ''Polygonum''
| image = Heliotropium curassavicum01.jpg
| image_width = 240px
| image_caption = ''Polygonum maritimum'', sea knotgrass
| regnum = [[Plant]]ae
| divisio = [[Flowering plant|Magnoliophyta]]
| classis = [[Dicotyledon|Magnoliopsida]]
| ordo = [[Caryophyllales]]
| familia = [[Polygonaceae]]
| genus = '''''Polygonum'''''
| genus_authority = [[Carolus Linnaeus|L.]]
| subdivision_ranks = [[Species]]
| subdivision =
Between 150-300 species; see text
}}

'''''Polygonum''''' is a [[genus]] in the [[buckwheat]] family [[Polygonaceae]]. The name is probably derived from the [[Greek language|Greek]] ''poly'', "many" and ''gonu'', "knee" in reference to the swollen jointed stem [[Node_(botany)|nodes]]. There is another theory which states that the second part of the name is derived from Greek ''gonos'', "children". Common names include '''knotweed''', '''knotgrass''', '''bistort''', '''tear-thumb''', and several others. In the [[Middle English]] [[glossary]] of [[herbs]] "[[Alphita]]" (ca. [[1400]]-[[1425]]), it was known as '''ars-smerte'''<ref>Middle English Dictionary.</ref>. There have been various opinions about how broadly the genus should be defined. [[Buckwheat]] for example has sometimes been included in the genus.

The genus primarily grows in northern [[temperate]] regions. They vary widely from prostrate [[herbaceous]] [[annual plant]]s under 5 cm high, others erect herbaceous [[perennial plant]]s growing to 3–4 m tall, and yet others perennial [[wood]]y [[vine]]s growing to 20–30 m high in [[tree]]s; several are also aquatic, growing as floating plants in [[pond]]s. The smooth-edged [[Leaf|leaves]] vary greatly in shape between species, and can be narrow lanceolate, oval, broad triangular, heart shaped or arrowhead shaped; they range from 1–30 cm long. The stems are often reddish or red-speckled. The [[flower]]s are small, pink, white, or greenish, forming in summer in dense clusters from the leaf joints or stem apices.

''Polygonum'' species are used as food plants by the [[larva]]e of some [[Lepidoptera]] species - see [[list of Lepidoptera which feed on Polygonum]], a number are considered weedy, especially in moisture retentive soils in the USA.

==Species==

Between 150–300 species are recognised depending on the circumscription of the genus; some [[botanist]]s divide the genus up into several smaller genera, including ''Fagopyrum'', ''Fallopia'' and ''Persicaria''. Selected species include:
*''[[Polygonum achoreum]]''
*''[[Polygonum acuminata]]''
*''[[Polygonum acuminatum]]''
*''[[Polygonum arenarium]]''
*''[[Polygonum arenastrum]]'' – [[small-leaved knotgrass]]
*''[[Polygonum argyrocoleon]]''
*''[[Polygonum arifolium]]''
*''[[Polygonum aviculare]]'' – [[common knotgrass]]
*''[[Polygonum bellardii]]''
*''[[Polygonum bidwelliae]]''
*''[[Polygonum bistortoides]]''
*''[[Polygonum bolanderi]]''
*''[[Polygonum boreale]]''
*''[[Polygonum brasiliensis]]''
*''[[Polygonum bungeanum]]''
*''[[Polygonum buxiforme]]''
*''[[Polygonum caespitosum]]''
*''[[Polygonum californicum]]'' – [[California knotweed]]
*''[[Polygonum careyi]]''
*''[[Polygonum cascadense]]''
*''[[Polygonum caurianum]]''
*''[[Polygonum chinense]]''
*''[[Polygonum coccineum]]''
*''[[Polygonum cognatum]]'' – [[Indian knotgrass]]
*''[[Polygonum davisiae]]''
*''[[Polygonum densiflorum]]''
*''[[Polygonum dibotrys]]''
*''[[Polygonum douglasii]]'' – [[Douglas' knotweed]]
*''[[Polygonum erectum]]''
*''[[Polygonum flaccidum]]'' – ([[Meissn.]])
*''[[Polygonum foliosum]]''
*''[[Polygonum forrestii]]''
*''[[Polygonum fowleri]]''
*''[[Polygonum franktonii]]''
*''[[Polygonum glaucum]]''
*''[[Polygonum griffithii]]''
*''[[Polygonum herniarioides]]''
*''[[Polygonum heterosepalum]]'' – [[dwarf desert knotweed]]
*''[[Polygonum hickmanii]]''
*''[[Polygonum hirsutum]]''
*''[[Polygonum hongkongensis]]''
*''[[Polygonum hudsonianum]]''
*''[[Polygonum hydropiperoides]]''
*''[[Polygonum lacerum]]''
*''[[Polygonum lanigerum]]''
*''[[Polygonum marinense]]''
*''[[Polygonum maritimum]]'' – [[sea knotgrass]]
*''[[Polygonum meisneranum]]''
*''[[Polygonum meisnerianum]]''
*''[[Polygonum minimum]]'' – [[broadleaf knotweed]]
*''[[Polygonum multiflorum]]''
*''[[Polygonum oxyspermum]]'' – [[Ray's knotgrass]]
*''[[Polygonum paronychia]]''
*''[[Polygonum paronychioides]]''
*''[[Polygonum parryi]]''
*''[[Polygonum patulum]]''
*''[[Polygonum perfoliatum]]'' – [[mile-a-minute weed]]
*''[[Polygonum phytolaccifolium]]''
*''[[Polygonum plebeium]]''
*''[[Polygonum polycnemoides]]''
*''[[Polygonum polycnenoides]]''
*''[[Polygonum polygaloides]]''
*''[[Polygonum punctatum]]''
*''[[Polygonum raii]]'' = ''[[Polygonum oxyspermum]]''
*''[[Polygonum ramosissimum]]''
*''[[Polygonum robustius]]''
*''[[Polygonum rurivagum]]''
*''[[Polygonum salicifolium]]''
*''[[Polygonum scoparium]]''
*''[[Polygonum segetum]]''
*''[[Polygonum setaceum]]''
*''[[Polygonum shastense]]''
*''[[Polygonum striatulum]]''
*''[[Polygonum tenue]]''

===Reclassified as ''Fagopyrum''===

*''Polygonum fagopyrum'' (''[[Fagopyrum esculentum]]'') – [[buckwheat]]

===Reclassified as ''Fallopia''===

*''Polygonum aubertii'' = ''Polygonum baldschuanicum''
*''Polygonum baldschuanicum'' (''[[Fallopia baldschuanica]]'') (''Fallopia aubertii'', ''Bilderdykia aubertii'', ''Bilderdykia balschuanicum'') – [[Russian vine]]
*''Polygonum cilinode'' (''[[Fallopia cilinodis]]'', ''Bilderdykia cilinodis'') – [[fringed black bindweed]]
*''Polygonum convolvulus'' (''[[Fallopia convolvulus]]'') – [[black bindweed]], wild buckwheat
*''Polygonum cuspidatum'' = ''Polygonum japonicum'' - [[Japanese knotweed]]
*''Polygonum dumetorum'' (''Fallopia dumetorum'') – [[copse bindweed]]
*''Polygonum japonicum'' (''[[Fallopia japonica]]'', ''Reynoutria japonica'') – [[Japanese knotweed]]
*''Polygonum multiflorum'' (''[[Fallopia multiflora]]'')
*''Polygonum sachalinense'' (''[[Fallopia sachalinensis]]'', ''Reynoutria sachalinensis'') – [[giant knotweed]]
*''Polygonum scandens'' (''[[Fallopia scandens]]'')

===Reclassified as ''[[Persicaria]]''===
[[Image:PolygonumPersicara-flower-sm.jpg|thumb|Flowerhead of ''Persicaria maculata'' (syn. ''Polygonum persicara'')]]

*''Polygonum affine'' (''[[Persicaria affinis]]'')
*''Polygonum alatum'' (''[[Persicaria alata]]'')
*''Polygonum alpinum'' – [[alpine knotweed]] (''[[Persicaria alpina]]'')
*''Polygonum amphibium'' – [[amphibious bistort]] (''[[Persicaria amphibia]]'')
*''Polygonum amplexicaule'' (''[[Persicaria amplexicaulis]]'')
*''Polygonum bistorta'' – [[bistort]] (''[[Persicaria bistorta]]'')
*''Polygonum campanulatum'' – [[lesser knotweed]] (''[[Persicaria campanulata]]'') (''Reynoutria campanulatum'')
*''Polygonum capitatum'' (''[[Persicaria capitata]]'')
*''Polygonum emodi'' (''[[Persicaria emodi]]'')
*''Polygonum filiforme'' (''[[Persicaria virginiana]]'')
*''Polygonum hydropiper'' – [[water-pepper]] (''[[Persicaria hydropiper]]'')
*''Polygonum lapathifolium'' – [[pale persicaria]] or nodding smartweed (''[[Persicaria lapathifolia]]'')
*''Polygonum longisetum'' (''[[Persicaria longiseta]]'')
*''Polygonum macrophyllum'' (''[[Persicaria macrophylla]]'')
*''Polygonum milletii'' (''[[Persicaria milletii]]'')
*''Polygonum minus'' – [[small water-pepper]] (''[[Persicaria minor]]'')
*''Polygonum mite'' – [[tasteless water-pepper]] (''[[Persicaria mitis]]'', ''Persicaria laxiflora'')
*''Polygonum molle'' (''[[Persicaria mollis]]'')
*''Polygonum nepalense'' (''[[Persicaria nepalensis]]'')
*''Polygonum odoratum'' – [[Vietnamese coriander]] (''[[Persicaria odorata]]'')
*''Polygonum orientale'' (''[[Persicaria orientalis]]'')
*''Polygonum pensylvanicum'' – Pennsylvania smartweed or pink knotweed or pinkweed (''[[Persicaria pensylvanica]]'')
*''Polygonum persicaria'' – [[Redshank (plant)|redshank]] or persicaria or lady's thumb (''[[Persicaria maculosa]]'')
*''Polygonum polystachyum'' = ''Polygonum wallichii''
*''Polygonum runciforme'' (''[[Persicaria runcinata]]'')
*''Polygonum sagittatum'' – arrowleaf tearthumb, American tear-thumb or scratchgrass (''[[Persicaria sagittata]]'')
*''Polygonum tenuicaule'' (''[[Persicaria tenuicaulis]]'')
*''Polygonum tinctorium'' (''[[Persicaria tinctoria]]'')
*''Polygonum vaccinifolium'' (''[[Persicaria vaccinifolia]]'')
*''Polygonum virginianum'' (''[[Persicaria virginiana]]'')
*''Polygonum viviparum'' – [[Alpine Bistort|alpine bistort]] (''[[Persicaria vivipara]]'')
*''Polygonum wallichii'' – Himalayan knotweed (''[[Persicaria wallichii]]'')
*''Polygonum weyrichii'' (''[[Persicaria weyrichii]]'')

==References/External links==
{{commons}}
*[http://internt.nhm.ac.uk/jdsml/nature-online/nature-navigator/ Website of the [[Natural History Museum]], London]
*[http://www.rhs.org.uk/RHSPlantFinder/plantfinder.asp Plant Finder section of the [[Royal Horticultural Society]]'s website]
*[http://www.habitas.org.uk/flora/index.html Flora of Northern Ireland]

==References==
{{Reflist}}

[[Category:Invasive plant species]]
[[Category:Polygonaceae]]

Knotweed - Revision history

MediaWiki default at 07:36, 16 October 2007