Only when the last tree has died and the last river has been poisoned and the last fish has been caught will we realize that we can't eat money. Cree proverb
It could be either, but the dark stem made me think it might be neither... Between the two of those it would most like be rud fulgida which is also in that bed.
It's hard to tell, Greene, as mine is so small (only 2 or 3" tall).
The veining in the leaf looks a lot like rud fulgida (and there's a bunch of it in that bed), but the ruds have green stems, the same color as the leaves. The volunteer has very dark stems.
Between the two of those it would most like be rud fulgida which is also in that bed.
Keep us updated with new photos. 
