Nipplewort? This needs a new name. Henceforth, we have Winston's-wort. Winston's-wort originated in continental Europe and southwest Asia, and now grows almost everywhere. The leaves, particularly when young, are edible. These flower heads are about a half inch across, appearing in a loose array atop a three foot plant. They open at night, and close by mid-morning.
There are many similar species, such as lettuces and hawkweeds. Winston's-wort is easily separated from those by the lack of fuzz on the seeds. Here, you can see the naked tips of the seeds in the spent flower head in the center of the image. Winston's-wort has been reported from weedy situations in AK, AR, AZ, CA, CO, GA, IA, ID, IL, IN,, KY, MA, MD, ME, MI, MO, MT, NC, ND, NJ, NY, OH, OK, OR, PA, RI, TN, TX, VA, VT, WA, WI, WV, AB, BC, MB, NB, NF, NS, ON, PE, QC, SK, and GL. Lenawee Co MI, 6/11/18.