The Polygonaceae are a family of flowering plants known informally as the knotweed family or smartweed—buckwheat family in the United States. The name is based on the genus Polygonum, and was first used by Antoine Laurent de Jussieu in 1789 in his book, Genera Plantarum.[2] The name may refer to the many swollen nodes the stems of some species have, being derived from Greek, poly meaning 'many' and gony meaning 'knee' or 'joint'. Alternatively, it may have a different derivation, meaning 'many seeds'.[3] The Polygonaceae comprise about 1200 species[4] distributed into about 48 genera.[5] - https://en.wikipedia.org/wiki/Polygonaceae
Cutting in June results in shortened regrowth (2 to 5 feet) and elimination of persistent stems from the previous season. This is a particular advantage in riparian settings, where full-size knotweed will hang over the water, making it impossible to treat without contacting the water with herbicide solution.
Use any of these glyphosate formulations to treat knotweed foliage, waiting eight weeks after cutting or a late frost to treat. The product rates differ because the glyphosate concentration differs between products. Applications of Aquaneat will require an additional surfactant (e.g., CWC 90). No additional surfactant is needed with Glyphomate 41. If you work at the early end of the operational window, you can make a touch-up application later in the season before a killing frost. - https://extension.psu.edu/japanese-knotweed