Yellow composites can be a pain to sort out, though dandelions are usually readily identified by their hollow leafless stems that exude a milky juice and their yellow heads which lack disc florets (that little central pad of florets that you see in daisies, sunflowers and the like). The hundreds of microspecies (the upshot of their peculiar sex lives) is another matter, though only Taraxacum-obsessives usually bother to delve. I find the "hawkish complex" (all those hawkweeds, hawksbeards, hawkbits and catsears) far more perplexing. You need a memory like an elephant's to remember which is which.