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Rithet's Bog LogoPoison Hemlock Alert

BARA Bugle (Broadmead Area Residents Association Newsletter),
Spring 2006 - Sharon Hartwell

Many people are aware of Giant Hogweed, the spectacular poisonous plant that Saanich Council recently listed under the Noxious Weeds Bylaw. But did you know about Poison Hemlock, the other, more toxic plant that was also added to the list? It is widespread in Greater Victoria and has been responsible for several deaths over the past twenty years. It grows at Rithet’s Bog, and has been observed at other locations in Broadmead.

How to recognize Poison Hemlock

Poison Hemlock (Conium maculatum), originally imported from Europe as a garden plant, is a member of the carrot family, like anise and dill. It produces rosettes of bright green, finely divided leaves in winter and spring, and then grows into a tall (up to 3 meters), multi-stalked plant with many clusters of tiny white flowers. Distinguishing features include purple blotches near the base of the hollow stems, and the noxious, acrid odor the plant produces when bruised or crushed. For photographs, please see http://www.psu.missouri.edu/fishel/poison_hemlock.htm

Toxicity and Treatment

All parts of this plant are poisonous: leaves, stems, roots, and fruits. It has been used as a poison since ancient times – Socrates was executed with a cup of Poison Hemlock tea. The active agents are volatile alkaloids, including coniine, which is curare-like, and acts by paralyzing the striated muscles. If a sufficient amount has been ingested, death takes place as a result of respiratory paralysis.

Poison Hemlock is so noxious tasting that an adult would not unintentionally consume enough to cause death. Unfortunately it is small children who are the usual victims; even a tiny piece of foliage eaten out of curiosity can be enough to cause serious poisoning. Treatment consists of stomach evacuation, and the administration of activated charcoal. In advanced cases, mechanical respiratory support may be necessary to prevent death.

Poison Hemlock does not need to be eaten to cause toxic reactions. Rashes and asthma have been reported in sensitive individuals who touched the plant or inhaled its volatile oils.

Methods of control – what to do if you discover it

If you discover Poison Hemlock on your property, it should be removed as soon as possible. The rosettes, including the large parsnip-like root, are relatively easy to dig out. If the plant is larger, the entire mass must be dug, cut down and carefully disposed of, taking care not to spread seeds. The best method of disposal is to bag and seal the plants and place in the garbage. Composting is not recommended, since Poison Hemlock remains toxic for several years after being pulled. Burning is also discouraged, as the volatile oils may be toxic if inhaled. Please exercise care when working with Poison Hemlock! Protect your hands and skin with gloves, long sleeves and pants, and wash your hands carefully after handling any part of this plant.

Controlling Poison Hemlock at Rithet’s Bog

RBCS volunteers spend many hours removing Poison Hemlock from Rithet’s Bog. If you would like to assist, we would welcome your help at one of our monthly work parties. Volunteer work parties to pull broom and dig noxious weeds are held from September to June on the first Sunday of each month, 1-3 p.m. Meet at the Fir Glen Tree entrance. Please contact us at info@rithetsbog.org or 250-479-0491.

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