The common name is somewhat deceptive since this is not our only sowthistle which is annual. It is most often confused with spiny sowthistle (Sonchus asper) which is mush more spiny. Spiny sowthistle has rounded auricles (ears) at the leaf bases, while those of annual sowthistle are pointed. Seedlings and young plants of this species often have watery juice, but mature plants have milky juice.