Q: There was no sign of this plant in Jan or Feb. Now it has been identified as Japanese Knotweed. It is on virtually every invasive species list in North America. It will soon be history in my yard!
A: You’re right on – it’s Polygonum cuspidatum, sometimes called Mexican bamboo. Although the wispy red flowers are sort of attractive in fall, it spreads like crazy and chokes out anything in its way.
If you get tired of digging it out, use an old kitchen peeler to slice off several strips of thin bark near the base and dab some undiluted glyphosate (Roundup, Kleenup, etc) on the wound.
By exposing the tissue inside the stem, the herbicide is absorbed faster.