Looks like Kerria Japonica.

Posted by jayco 5b NY (My Page) on Mon, Jun 3, 13 at 15:07

Thank you so much for the answer. I did not realize they are so cold hardy!

This is actually a bush, with a running habit. Came back for 3 years from the roots.

This post was edited by wieslaw59 on Mon, Jun 3, 13 at 19:14

You're welcome! Yes, they are tough plants and wieslaw is right, it's a shrub and will get rather large.

Just to clear things up: the white part is a sun burn. It is all yellow in shade.

It definitely looks like Kerria japonica however mine was always in mostly shade and bloomed just yellow. It was reliably hardy in my then-Zone 5b garden. It grew larger year after year but never seeded around and after 20+ years was still what I would categorize as a well-behaved perennial shrub. It was never bothered by pests in my experience.