This plant was found in our vegetable garden and we transplanted it to our flower garden to watch it and see if we could figure out what it is. While transplanting it we noticed it has a tap root. Since transplanting it, it has grown flowers but we still don't know what it is.
O'Brien County Iowa
This is Yellow Salsify, Tragopogon dubius. Don't let it seed. Here is a page from the US Forest Service, with lots of information about the plant: http://www.fs.fed.us/database/feis/plants/forb/tradub/all.html