This species is a very prickly annual with clasping stem leaves and milky juice. It is one of the very few yellow flowered `thistles.` It can easily be confused with annual sowthistle which is also prickly, but much less so than prickly sowthistle. Annual sowthistle has pointed auricles (ears) at the leaf bases, while those of prickly sowthistle are rounded. Seedlings and young plants of this species often have watery juice, but mature plants have milky juice.