willow-weed, Persicaria lapathifolia

Willow-weed is very similar to lady's-thumb, but more nodding, and it grows in places that are more damp. It is native - almost everywhere. The critters that eat the seeds have spread it around the globe. But it was challenged by dry places. Ever have something you can't or shouldn't do on your own? So you got together with a friend and just said, "Let's do it!" That's what willow-herb did to take advantage of those dry places. It got together with another species and parented lady's-thumb. Now willow-weed genes really are pretty much everywhere. The only state or province willow-weed doesn't grow in is HI. It's also on GL and SPM. Ives Fen Preserve, Lenawee Co MI, 8/29/10. Knotweed family, Polygonaceae.