Knotgrass
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Knotgrass".

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Polygonum
Polygonum coccineum.
Polygonum coccineum.
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Caryophyllales
Family: Polygonaceae
Genus: Polygonum
L.
Species

Between 150-300 species; see text

Polygonum is a genus in the buckwheat family Polygonaceae. Common names of polygonum species include knotweed, knotgrass, bistort, tear-thumb, mile-a-minute, and several others. In the Middle English glossary of herbs "Alphita" (ca. 1400-1425), it was known as ars-smerte[1]. 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 plants under 5 cm high, others erect herbaceous perennial plants growing to 3–4 m tall, and yet others perennial woody vines growing to 20–30 m high in trees; several are also aquatic, growing as floating plants in ponds. The smooth-edged 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 flowers are small, pink, white, or greenish, forming in summer in dense clusters from the leaf joints or stem apices.

The genus name is traditionally believed to be derived from the Greek poly, "many" and gonu, "knee" in reference to the swollen jointed stem nodes, but grammatically gone means "seed"[2]

Polygonum species are used as food plants by the larvae of some Lepidoptera species - see list of Lepidoptera that feed on Polygonum, a number are considered weedy, especially in moisture retentive soils in the USA.

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Distribution and Uses

At least one species has been eaten during times of famine.[3]

Species

Between 65[2]–300 species are recognised depending on the circumscription of the genus; some botanists divide the genus up into several smaller genera, including Fagopyrum, Fallopia and Persicaria.

The genus Polygonella has a number of morphological similarities with Polygonum and some authors have included Polygonella in Polygonum.[2]

Selected species include:

Reclassified as Fagopyrum

Reclassified as Fallopia

Reclassified as Persicaria

Flowerhead of Persicaria maculata (syn. Polygonum persicara)
Flowerhead of Persicaria maculata (syn. Polygonum persicara)

References/External links

Wikimedia Commons has media related to:

References

  1. ^ Middle English Dictionary.
  2. ^ a b c "Polygonum". Flora of North America.
  3. ^ Łukasz Łuczaj (2008). "Archival data on wild food plants used in Poland in 1948". J Ethnobiol Ethnomed 4 (4): 4. doi:10.1186/1746-4269-4-4. PMID 18218132. PMCID: PMC2275233. 
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