Knotgrass or knot grass is the common name for several plants and a moth and may refer to:
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Paspalum distichum
''Paspalum distichum'' is a species of grass. Common names include knotgrass, water finger-grass, couch paspalum, eternity grass, gingergrass, and Thompson grass. Its native range is obscure because it has long been present on most continents, an ...
'', a species of grass
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Polygonum
''Polygonum'' is a genus of about 130 species of flowering plant in the buckwheat and knotweed family Polygonaceae. Common names include knotweed and knotgrass (though the common names may refer more broadly to plants from Polygonaceae). In the ...
'', a genus of plants in the buckwheat family, more often known as knot weed
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Acronicta rumicis
''Acronicta rumicis'', the knot grass moth, is a species of moth which is part of the genus ''Acronicta'' and family Noctuidae. It was first described by Carl Linnaeus in his 1758 10th edition of ''Systema Naturae''. It is found in the Palearct ...
'', a moth of the family Noctuidae
{{Plant common name