Summary:
Fallopia sect. Parogonum has been recognized as its own genus, Parogonum, within subtribe Reynoutriinae.

Fallopia ciliinodis and Fallopia cynanchoides are now Parogonum ciliinode and Parogonum cynanchoides, respectively.

Flag:
https://www.inaturalist.org/flags/665893.

POWO:
https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77315139-1
https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77315140-1
https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:77315141-1

Paper:
New insights into the phylogenetic relationships of Japanese knotweed (Reynoutria japonica) and allied taxa in subtribe Reynoutriinae (Polygonaceae) -- 2023 -- Stuart Desjardins et al.
https://doi.org/10.3897/phytokeys.220.96922