Shade Gardening: virginia knotweed, 1 by Weerobin

Weerobin wrote:
I need some info about virginia knotweed.

I have a couple patches, courtesy of some passing bird, I guess, since I didn't plant them.
They're the generic variety with the maroon chevron on the leaves.
They are blooming now.
I first noticed them the last year or two, but this year they've spread in a couple places to sizable patches.
I think they look nice.

Are they invasive?
I'm always suspicious when I see something thriving in my yard that it must be invasive.
Here's one patch.