Polygonum is a genus in the Polygonaceae family. Common names include knotweed, knotgrass, bistort, tearthumb, mile-a-minute, smartweed and several others. In the Middle English glossary of herbs Alphita (c. 1400-1425), it was known as ars-smerte. There have been various opinions about how broadly the genus should be defined. For example, Buckwheat has sometimes been included in the genus.The genus primarily grows in northern temperate regions.