Looks to me like Baptisia, False Indigo. But mine doesn't self-seed at all, so maybe not.

Here is a link that might be useful: false indigo

Looks like some kind of Thermopsis,
did you ever see it flower?
A better photo would help, and one of the flower even more :-)

Here is a link that might be useful: something like this

Picture 1

Picture 2

And here is the third picture. So the seeds are encapsulated just like peas :).

Any other ideas on what this could be?

Thanks a ton!!

ottawavalleygardener: IT is the baptisa you mentioned. When I looked at the pics, the flowers and the seeds matched. I now remember there were flowers in early spring :)

This one rapidly spreads though.

Thanks :)