Ask Mr. Smarty Plants

Poison hemlock (Conium maculatum) is not a North American native plant (it is from Europe, North Africa and West Asia) but is a very noxious plant found naturalized along many roadsides or open fields in Asia, North America, Australia and New Zealand. It is not related to the native tree called hemlock (Tsuga canadensis). Poison hemlock is a member of the parsley family and has similarities to Queen Anne's lace (Daucus carota) and American wild carrot (Daucus pusillus). It can grow very tall (to 8 ft) - especially if moist. The plant has hollow stocks with large umbel-shaped flower clusters. Poison hemlock flowers in late spring (while wild carrot blooms later in summer).  Poison hemlock is toxic to animals and humans with symptoms appearing within three hours of ingestion. All parts are poisonous (even the brown, dead stems for years afterward). Avoid eating the plant or getting the plant sap on your skin. Symptoms are serious and sometimes deadly. Immediate medical attention should be given as the poison is fast acting. Approach it with extreme caution.

To see pictures of the plant at different life stages of poison hemlock visit the King County Noxious Weeds webpage for Poison-Hemlock. There are many look alikes including giant hogweed (Heracleum mantegazzianum), cow parsnip (Heracleum maximum), purple-stemmed angelica (Angelica atropurpurea), spotted water hemlock (Cicuta maculata), and wild parsnip (Pastinaca sativa). A good reference to see the various similar looking plants is Giant Hogweed and Look-a-Likes.