This did not look like a typical Sonchus to me but...all ray flowers and white latex=Lactuceae; Pappus is beakless and consists of some long bristles and lots of fine, long hairs. Achene is flattened with several nerves and roughened surface; leaves are clasping and auricled. I found the little stipitate glands on the peduncle interesting-haven't seen those mentioned anywhere.
Growing in the shade of a large Eastern Red Cedar. Achenes are 3-sided, perigynia are minutely pubescent at 25X magnification, and are not concealed by scales.
Flowers are sweet smelling, +/-35 per umbel, leaves ca. 2mm wide and all basal, spathe in 2-3 segments, each with 7 nerves