Garlic Mustard (Alliaria petiolata), fam. Brassicaceae.
Grows in the forest, in quite humid places. According to literature, these greens have garlic smell and may be consumed as food in limited quantities. From personal observations, its taste is somewhat inferior to garlic. It may be harmful in large quantities (analogous to garlic, radish, and all those plants with pungent sulfur compounds).