Do you have additional images of this plant? This looks more like Garlic Mustard, Alliaria petiolata, to me. Here are a couple of links with images for comparison.
http://www.kingcounty.gov/environment/animals-and-plants/noxious-weeds/weed-identification/garlic-mustard.aspx
https://en.wikipedia.org/wiki/Alliaria_petiolata
http://plants.usda.gov/core/profile?symbol=alpe4
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