Your mystery seedling looks like datura to me. Sometimes called Jimson weed, I have read that it spread across the continent starting in Jamestown settlement. It has a strange, musky scent and some folks are allergic to it, so don't touch its leaves without gloves. It's roots are almost impossible to dig if you let it attain full growth. It is a deadly poison, and we have had several residents at the drug rehab school in our valley who found some and then had to be life-flighted out. David Ehrlich wrote: > I have a strange weed growing in one of my pots. I'm pretty sure it's a Datura, > but I don't know what species, nor how its seed got into my pot as no Datura is > native to this part of the S.F. Peninsula. > > I combined the photos and gab into a blog which can be accessed at > http://mysterynightshade.blogspot.com/ > >