Blue Lettuce

Now I'm not sure if this is Blue Lettuce or Chickory! Guess I'll have to do a bit of Googling! Found this afternoon in Glennfield, Fish Creek Park, in the middle of a flat open area of tall grass. Just read on one website: "This plant can be confused with Tall blue lettuce (Lactuca biennis), or Prickly lettuce (Lactuca serriola) or Chicory (Chichorium intybus)." Any confirmation or correction of my ID attempt would be gratefully accepted!