Many capitulums, several corymbs with capitulums as the end nodes of each corymb, or one compound corymb with capitulums as the end nodes?
The scientific name of common sowthistle is Sonchus oleraceus, which seems not the same as the one on the link(Sonchus Linnaeus). But that is not important(they seem to have the same kind of inflorescence). The important thing is that it says "Heads borne in corymbiform to subumbelliform arrays" . So, I'm still not clear which inflorescence it has.
Sonchus oleraceus is the scientific name of the species; Sonchus is the name of the genus it is in, and Linnaeus is the person who named it. So they're talking about the same thing. Basically: a variable and fairly complex inflorescence!
