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Wisconsin Plant of the Week

Cicuta maculata L.

Apiaceae (Parsley Family)

Common Name:

spotted water hemlock


The most poisonous plant in North America, water hemlock is a native perennial with thick taproots.  It's found in wet meadows, woods edges and marshes growing from 1 to 2 m tall.

Members of the Parsley Family are easy to recognize. Most have small 5-parted flowers, usually white or yellow, arranged in clusters called umbels, i.e. individual flowers are on stalks arranged like the spokes of an umbrella. The ridged stems are hollow between the nodes; the leaves are alternate, usually divided, and the base of each leaf stalk ends in a sheath that surrounds the stem.  Both the foliage and the seeds have oils that are aromatic.

Like the flowers of cowbane and water parsnip, which grow in similar habitat, the umbels of Spotted Water Hemlock are divided into smaller umbels, or “umbellets”. Individual flowers are about 2 mm and the umbels are nearly flat and 4 to 8 cm across. They bloom from June through September.

Hemlocks are distinguished in that the veins in the leaves end in the sinuses between the teeth, rather than at the teeth. Spotted Water Hemlock leaves are 2 or 3 times divided into lance-shaped leaflets, most of which are coarsely toothed.  The stem is a mottled purple, or (as in the photo) green with purple nodes.

Voss describes the poison, the hemlock that Socrates drank, " . . . concentrated in the clustered tuberous roots, which one will not mistake for parsnips more than once. . . symptoms include abdominal pain, convulsions, fever, paralysis and respiratory failure, followed by death -- sometimes within 15 minutes . . . "

  • Origin of the name: Cicuta, L.,  hemlock; maculata, L., spotted, blotched, refers to the stem
  • Range:  Throughout N. Amer.
  • WI Range:  Statewide
  • Common associates: Horsetails, Marsh Milkweed, Skunk Cabbage
  • Wetland Indicator Status: OBL
  • Coefficient of Conservatism: C = 6 (S&W), C = 4 (MI)
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