Could be several things. You shold let one go to seed and post a picture of the seed head - that would be the best way to get an ID. Also would help to know your location.
This post was edited by hortster on Mon, Jun 2, 14 at 15:43
Oh great-I thought maybe someones dianthus seed blew over here. I just yanked it all and tossed it. like there aren't enough weird weeds this year. At least it comes out easy.