This species is very similar in appearance to the poisonous water hemlock. The main distinguishing characteristic of western water hemlock is its toxicity. Another reliable method to identify water hemlock is to examine the leaf veins. Cicutoxin is found in five species of water hemlock, all belonging to the family Apiaceae. Similarly, the plant should not be confused with "cicuta" (commonly known as water hemlock). It resembles the highly toxic poison hemlock and water hemlock. Cicuta douglasii, the western water hemlock, is a poisonous plant in the family Apiaceae. It is easily confused with the highly toxic water hemlock ("Conium maculatum"). Water hemlock also has a large swelling at the stem base which water parsnip lacks. All water hemlock and poison hemlock are highly poisonous, but water parsnip is not.