It's neither of the two Scutellaria on this site ..
http://www.thewildflowersociet...
I would wait until it flowers, the leaves look a little like Viola. I have a lot of new self sets recently started to flower, they are small flowers on tallish plants which I get here and there from the wild Viola tricolor seemingly crossing with others I have grown years ago. Having said that, something about the form of your plant doesn't seem to fit.
I just noticed, it looks to have square stems which would place it in Lamiaceae.
