Japanese Knotweed

Your plant appears to be Japanese knotweed, an aggressive weed that is difficult to eradicate. You’ll need to dig up every last bit of root. Then, as bits of root you miss send up new leaves, dig those out too. You can win against this plant – in the long run! Mowing or cutting back greatly reduces the strength of this perennial plant (at any season). Preventing those blooms from going to seed will reduce next year’s “crop” of weeds. And after cutting back (or over the winter), try covering the area with cardboard, or several layers of newspaper. Water well and mulch over top of this, and keep an eye out for rogue sprouts appearing in spring. If you choose to apply herbicide, this is one of the best times of year to do it.