Ministry of Agriculture

Western Water-Hemlock (Cicuta douglasii)

Western water-hemlock (Cicuta douglasii) is a highly toxic, native member of the Parsnip Family. Western water-hemlock is found in sloughs, wet meadows, along streambanks and other wet areas throughout British Columbia. This plant is poisonous to all types of livestock and to humans. The onset of symptoms is so rapid that treatment is not usually successful.

The toxins are concentrated in the chambered rootstock but also occur in the leaves and stems as well. A consumption of 0.1% of body weight of the green material (leaves and stems) is lethal, however, the oil in a single bulb is enough to kill a 1600 pound cow.

Western water-hemlock is the most common of three native species of water hemlock that occur in British Columbia. Other species include:

  • Spotted water-hemlock (Cicuta maculata) - also highly poisonous, and occurs east of the Cascade Mountains north to Alaska;
  • Northern water-hemlock (Cicuta virosa) - rare in B.C.; slightly less toxic but can still cause poisoning.

Similar plants include:

  • Cow Parsnip (Heracleum lanatum) - grows in uplands, up to ten feet tall, large maple-like leaves;
  • Angelica (Angelica spp.) - uplands and lowlands; and
  • Water Parsnip (Sium suave) - very similar ecology to western water-hemlock.

Identification of Western Water-Hemlock Versus Water Parsnip

Bulb

Western water-hemlock bulb Water parsnip bulb

Western water-hemlock has an asymmetrical bulb with narrow chambers containing a clear oil (cicutoxin) which turns bright orange when it is exposed to air. The bulb has fleshy side roots that allow the bulb to float in times of high water.
Water parsnip has a symmetrical root with large chambers containing no oil, and it has fibrous roots which anchors the bulb into the soil.

Leaves

Western water-hemlock leaves Western water-hemlock leaves.
Arrow indicates veins ending at the notches of the leaf margins.
Water parsnip leaves

Western water-hemlock has compound leaves with the veins usually ending in the notches along the leaf margins.
Water Parsnip has a simple, opposite leaves with the veins ending at the leaf tips.

Flower Head

Western water-hemlock flower Water parsnip flower

Western water-hemlock has white to greenish-coloured flowers formed in a compound umbel (umbrella-shaped flower head); it is bractless (no leaves at base of flower heads).
Water parsnip has white-coloured flowers formed in an umbel; it has bracts (leaves at base of large umbel and at base of small umbels making up the flower head).


For More Information
Ken Awmack
Resource Development Agrologist
Ministry of Agriculture
Williams Lake, B.C.
250 398-4500