Persicaria virginiana.

a/k/a painter's pallette and jumpseed, this is a cultivar of Japanese knotweed. It is not as invasive as the knotweed, but has been reported by many as being very ... shall we say "aggressive." If you decide to keep it, keep a close watch on it.

And, as long as you're in the Native Plants forum, to be honest, I would remove it ... along with the ivy seen in the background. Years ago I allowed some to stay in a very difficult area and it has become a most unwelcome guest, always trying to exceed the bounds I set for it. Both English and Boston ivy have made several invasive plant and "do not plant" lists.

This post was edited by agardenstateof_mind on Tue, Aug 6, 13 at 19:49

Japanese knotweed is Fallopia japonica, a different species altogether. Persicaria virginiana is native to North America, although the wild form lacks the chevrons on the leaves.

Then this is a non-native relative of a native plant called Persicaria Virginiana? Is it an invasive that should be removed?

No, it is just a color variant of P. virginiana, not a relative of it. It is native. It's up to you whether or not to keep it. In the wild it is a plant adapted to disturbed places like trails and floodplains, so it could potentially spread rapidly in a garden. It's isn't invasive though.

Sorry, I relied on information from the Missouri Botanical Garden and the University of Rhode Island.