[3] The genus is native to temperate and subtropical regions of the Northern Hemisphere, but species have been introduced elsewhere.

[5][6] He was the superintendent of the botanical garden at Padua and an acclaimed anatomist, being considered a founder of modern anatomy.

For example, Meissner in 1856 placed both Adanson's Fallopia and the genus Reynoutria in a broadly defined Polygonum, as did Bentham and Hooker in 1880.

When the genus Fallopia was recognized, as was generally the case from the 1970s onwards, Reynoutria was sometimes included and sometimes not.

[8] Subsequent molecular phylogenetic studies have confirmed the separation of Fallopia from other related genera.

Within the tribe, it is most closely related to the genera Reynoutria and Muehlenbeckia, forming the so-called "RMF clade".

The hybrid, ×Reyllopia conollyana (J.P.Bailey) Galasso (Reynoutria japonica × Fallopia baldschuanica) is called railway-yard knotweed.