That would be Japanese Knotweed. The existence of this scourge should convince everyone, including Ken Ham, that there is no intelligent designer. Its existence in Japan was tolerable because, naturally, since it's indigenous to the islands there are many insects and other creatures there that eat it. But in Europe and North America, there aren't any, not a single one.
The plant spreads vegetatively, via rhizomes. It outcompetes every other plant, and it forms dense thickets where nothing else can grow. It is extremely vigorous and thrusts up through gaps between paving blocks, destroys roads and oh yeah, destroys the foundations of houses. It is extremely difficult to eradicate because it grows back from the rhizome and if you leave even 1/2 inch, it will reappear. It is particularly fond of riverbanks and can totally destroy riverine habitats.
This is what it looks like when it newly sprouts:
And here's what it looks like in bloom.
If you have knotweed on your property, your real estate is literally unsaleable. Eradicating it takes years. You have to keep cutting it down and poisoning it, over and over. If you see any, start killing it now, and expect you will be devoting yourself to the project for a long time to come. Most homeowners, we are told, will be unable to cope with a large infestation themselves and will need to hire expert help.
The bad news for me is that there are extensive stands along the state road near the center of my tiny little town. The biggest stand is on the edge of a cornfield, which makes me wonder if the farmer has all his marbles. I haven't seen any in my neck of the woods but presumably we will at some point.
Gypsy moths, Russian olives, barberry, Asian long-horned beetles, emerald ash borers, woolly adelgids, knotweed -- who knows what these woods will look like in 20 years. I think we have no choice but to try to fight back by introducing natural enemies of these pests. Yeah, maybe that will backfire but I don't see how it can make things any worse.