AskDefine | Define knotgrass

Dictionary Definition

knotgrass n : low-growing weedy grass with spikelets along the leaf stems [syn: Paspalum distichum]

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.


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


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