I'll jump in with both feet and say that I "think" it is a weed. I've got something here that looks like this and when it comes through the ground, the leaves are looking skyward. Seems to come up everyplace some years and other years, nothing. Last year I had tons of them and this year I'm saved from pulling and hoeing them out. Have no idea what they are, but I knew I didn't plant them. Remember, I could be totally wrong, so if no one knows, I'd let them grow a while. Sometimes you can tell if they are weeds or not by crushing the leaves and smelling.