Family:Composite or Sunflower (Compositae)
Size: To 1.25 in.
Notes: Naturalized from Europe. 2 species of Sonchus in Arizona.
Spiny sowthistle entry in the online edition of An Illustrated Guide to Arizona Weeds, Kittie F. Parker, University of Arizona Press.
This plant is found on the Appleton-Whittell Research Ranch Working Check list of flora.
Entry for sowthistles in the University of California Statewide Integrated Pest Management Project.