Update: this was definitely japanese knotweed. I went back this spring and there was lots more of it. Dug up as much root as I could and will revisit periodically to get any regrowth. It was not as robust as it might have been due, I suspect, to the level of shade.

JW has large, unlobed, heart-shaped leaves and hollow cane-like stems And does produce an aggressively creeping rootstock instead of a tight clump of growth. As an aside the common nuisance kind in some areas - including much of the Pacific Northwest and Great Britain - is Bohemian knot-weed rather than Japanese. It is an intermediate hybrid resulting from the crossing of Japanese and giant knot-weeds, with the hybrid plants often being male. So that there is not a problem with these male plants reseeding. Just covering large spaces with their vegetative growth if they are not destroyed. I have seen uncontrolled patches in my area occupying square footage the size of entire building lots - and bigger. If still nobody has done anything about it there is an infested bottom-land in the bend of a river in a National Forest east of here that may be something on the order of an acre in extent.

Thanks for sharing. Terrible stuff. I wonder if there's a way to use the fact that virtually one cloned plant has spread through G.B. to our advantage to eradicate it? One genetic type could mean one effective weakness. I've read opinions from gardening types in the past who take the stance, 'nature will evolve and adapt, this is how evolution works,' while glibly ignoring a human-driven, devastating, massive extinction of richly bio-diverse life that will take thousands upon thousands of years to reattain. Seriously, how selfish can people be? At any rate, we have a lot of work ahead of us.

Yeah, it's everywhere. Starting a few years ago, the electric company started coming through and chopping down every tree along the street. They had been really taken to task for their awful response to one of the hurricanes, and their answer is to take down every tree within so many feet of the power lines. It's horrible the way they've absolutely ravaged some streets - and still doing it. Anyway, since they took down soooo many trees, well, guess what popped up in the newly-cleared, very sunny spots? Every weed and most invasives known to man. So you drive down the street and any frontage that isn't specifically a front yard, and even some that are (I live in a rural suburban area so lots of swaths of woods, large wooded side yards, still some farmland - all land that is not "tended") - so all this frontage is at the moment ablaze with japanes knotweed in bloom. It really is discouraging. :) Dee