Looks like a picture from areas of my yard. Garlic Mustard, a bi-annual weed. Despicable stuff. In the first year they create these little crowns, no blooms. Second year is when the shoot up and set seeds. You want to avoid getting to that stage.

The plants suppress growth of other seedlings and will crowd out most other vegetation. Buckthorn seedlings seem to live though, go figure.

I am hand-pulling mine, since they are growing in an area with runoff potential into pond. Four garbage bags alone today (since they are in the beginning stages of setting seed).....

Thanks for the quick ID! Now that you named it, I see I do have some in my yard, too, especially in wooded sections near our lawn. Mine is flowering and I did hand pull some of them, but there are probably many I missed.
Marcia