AskDefine | Define knotweed

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English

Noun

  1. Any of several plants of the genus Polygonum, with jointed stems and inconspicuous flowers

Derived terms

Extensive Definition

Polygonum is a genus in the buckwheat family Polygonaceae. The name may be derived from the Greek poly, "many" and gonu, "knee" in reference to the swollen jointed stem nodes. There is another theory which states that the second part of the name is derived from Greek gonos, "children" or gone, "seed". 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.
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.

Distribution and Uses

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

Species

Between 65–300 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.
Selected species include:

Reclassified as Fagopyrum

Reclassified as Fallopia

Reclassified as Persicaria

References

knotweed in Danish: Pileurt
knotweed in German: Vogelknöteriche
knotweed in Spanish: Polygonum
knotweed in Esperanto: Poligono
knotweed in Persian: علف هفت‌بند
knotweed in French: Renouée
knotweed in Japanese: タデ属
knotweed in Korean: 싱아
knotweed in Lithuanian: Takažolė
knotweed in Dutch: Duizendknoop
knotweed in Polish: Rdest
knotweed in Portuguese: Polygonum
knotweed in Finnish: Tattaret
knotweed in Turkish: Madımak (bitki)
knotweed in Ukrainian: Гірчак (рослина)
knotweed in Chinese: 蓼
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