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Polygonum aviculare 4.JPG
Polygonum aviculare
Scientific classification e
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Order: Caryophyllales
Family: Polygonaceae
Subfamily: Polygonoideae
Genus: Polygonum

See text.

Polygonum is a genus of about 130 species of flowering plant in the buckwheat and knotweed family Polygonaceae. Common names include knotweed and knotgrass. In the Middle English glossary of herbs Alphita (c. 1400–1425), it was known as ars-smerte.[1] There have been various opinions about how broadly the genus should be defined. For example, buckwheat (Fagopyrum esculentum) has sometimes been included in the genus as Polygonum fagopyrum. Former genera such as Polygonella have been subsumed into Polygonum; other genera have been split off.

The genus primarily grows in northern temperate regions. The species are very diverse, ranging from prostrate herbaceous annual plants to erect herbaceous perennial plants.

Polygonum species are occasionally eaten by humans, and are used as food plants by the larvae of some Lepidoptera species – see list. Most species are considered weedy, especially in moist soils in the USA.


When the genus is defined narrowly, Polygonum species are annual or perennial herbaceous plants, rarely shrubby, with much branched stems. The leaves are arranged alternately, usually less than 2 cm (0.8 in) long, with a length greater than the width. They have a membranous ochrea (a sheath around the stem nodes). The flowers are usually bisexual, rarely unisexual, and have five (occasionally four) tepals, the outer being slightly different from the inner ones. There are usually four to six stamens and three (rarely two) styles. The fruit is three-sided.[2]


The genus Polygonum was first described by Carl Linnaeus in 1754. The genus name is usually said to be from the Greek πολυ- (poly-, 'many') and γόνυ (gonu, 'knee' or 'joint'), in reference to the swollen jointed stem.[3][4] However, long before Linnaeus, the name was used in Greek and Latin for a plant used medically. Discussing the plant he knew as polygonum in 1655, Matthias Martinius referred to Scribonius Largus (who wrote a list of prescriptions around 47 AD) and gave an alternative etymology, based on γόνος (gonos, 'offspring', 'seed'), the meaning of the name then being the Latin foecundus, i.e. 'fecund', 'with many offspring'.[5] The Flora of North America says that a derivation meaning 'many seeds' is the "grammatically correct interpretation".[6]

Many members of the family Polygonaceae that are now placed in separate genera were at one time or other placed in Polygonum, including species of Fagopyrum, Fallopia, Persicaria and Reynoutria,[7] and older sources frequently use much wider definitions of the genus. Molecular phylogenetic studies, particularly in the 21st century, have led to major changes. Clarifying the circumscription of genera split from Polygonum was described in 2015 as "still ongoing".[7]

Classification and phylogeny[edit]

Polygonum is placed in the tribe Polygoneae of the subfamily Polygonoideae. Within the tribe, it is most closely related to the genera Duma and Atraphaxis, forming the so-called "DAP clade".[7]



Polygonum ciliinode (syn. Fallopia ciliinodis)

DAP clade




RMF clade



Fallopia s.s.


Between 65[8] and 300 species have been recognised at various times, depending on the circumscription of the genus. A number of species that had been included in Polygonum have been moved into several other genera, including Bistorta, Fagopyrum, Fallopia, Koenigia, Persicaria and Reynoutria. Other genera, such as Polygonella, have been subsumed into Polygonum.

As of February 2019, Plants of the World Online accepted 129 species.[9]

Reclassified species[edit]

Many species formerly placed in Polygonum have been moved to other genera in the subfamily Polygonoideae. Some synonyms are listed below.[10]

Polygonum species that have been reclassified as Bistorta[edit]

Polygonum species that have been reclassified as Fagopyrum[edit]

Polygonum species that have been reclassified as Fallopia[edit]

Polygonum species that have been reclassified as Koenigia[edit]

Polygonum species that have been reclassified as Persicaria[edit]

Polygonum species that have been reclassified as Reynoutria[edit]

Unresolved species[edit]


Several species can be eaten cooked,[11] for example during famines.[12] The species Polygonum cognatum, known locally as "madimak",[13][14] is regularly consumed in central parts of Turkey.

Care should be taken not to confuse Polygonum with Polygonatum – an entirely different genus of plants.

References in literature[edit]

In The Man Who Laughs Victor Hugo wrote of the Comprachicos (child-buyers) who created artificial dwarfs, formed "by anointing babies' spines with the grease of bats, moles and dormice" and using drugs such as "dwarf elder, knotgrass, and daisy juice". The idea of such use was also known to Shakespeare, as Beatrice K. Otto pointed out, quoting A Midsummer Night's Dream:[15]

Get you gone, dwarf;
You minimus, of hindering knot-grass made;


  1. ^ Middle English Dictionary
  2. ^ Nogueira, I.; Ortiz, S. & Paiva, J.A.R. (2006). "Polygonum L.". Flora Zambesiaca (online). 9. Royal Botanic Gardens, Kew. Retrieved 2019-04-29.
  5. ^ Martinius, Matthias (1655). "Polygonum". Lexicon Philologicum præcipue etymologicum et sacrum (in Latin). T. M. Goetzenius. Retrieved 2019-05-10.
  6. ^ Costea, Mihai; Tardif, François J. & Hinds, Harold R. "Polygonum". In Flora of North America Editorial Committee (ed.). Flora of North America (online). eFloras.org. Retrieved 2019-05-10.
  7. ^ a b c Schuster, Tanja M.; Reveal, James L.; Bayly, Michael J. & Kron, Kathleen A. (2015). "An updated molecular phylogeny of Polygonoideae (Polygonaceae): Relationships of Oxygonum, Pteroxygonum, and Rumex, and a new circumscription of Koenigia". Taxon. 64 (6): 1188–1208. doi:10.12705/646.5.
  8. ^ "Polygonum". Flora of North America.
  9. ^ "Polygonum: accepted species". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2019-02-28.
  10. ^ "Search for Polygonum species". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 2019-02-28.
  11. ^ Knotweed at NorthernBushCraft
  12. ^ Łukasz Łuczaj (2008). "Archival data on wild food plants used in Poland in 1948". J Ethnobiol Ethnomed. 4 (1): 4. doi:10.1186/1746-4269-4-4. PMC 2275233. PMID 18218132.
  13. ^ See the preparation of one particular dish in Turkey using Polygonum cognatum: https://www.youtube.com/watch?v=DzNCO94rWXE
  14. ^ One more dish based on "madimak" polygonum cognatum: https://www.youtube.com/watch?v=p3cJk6ChPkY

External links[edit]