Water Hemlock: Dangerous Plants for Dogs · The Wildest

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Water Hemlock: Dangerous Plants for Dogs

Pet parents watch out this summer for a common, but deadly plant

by JoAnna Lou | expert review by Dr Sam Wheelwright BVSc MRCVS
30 October 2023
dog playing in a pond
Photo: Rafael Shiga / Unsplash

If you’re hanging out with your dog by the water this summer, keep a watchful eye out for the common but extremely lethal plant water hemlock. It’s found all over the UK and can kill quickly, so its no joke.

Water hemlock, also known as hemlock water-dropwort or ‘dead man‘s fingers’, has been linked to several dog deaths in Northern Ireland as recently as this year. Its the most poisonous herb in the UK and common along most waterways.

What is water hemlock toxicity?

Water hemlock (Oenanthe crocata) is highly toxic to both people and pets. The plant contains the poisonous chemical oenanthotoxin, which has a sweet, parsely-like odour and affects the brain and central nervous system if ingested. Just a few leaves of water hemlock can kill a dog within hours, making it one of the most lethal plants on this continent.

The plant prefers moist surroundings and grows near bodies of water, like rivers, streams, ponds and in damp meadows.

If water hemlock is consumed, symptoms begin within a matter of minutes and include drooling, muscle twitching, seizures, and dilated pupils. This quickly turns into respiratory paralysis and then death. If a non-lethal dose is consumed by dogs, there is a chance at recovery, but there may be temporary or permanent damage to the heart or skeletal muscle.

Signs of water hemlock poisoning in dogs

  • excessive salivation and frothing

  • muscle twitching

  • dilation of the pupils

  • rapid pulse

  • rapid breathing

  • tremors

  • violent convulsions, grand mal seizures

What does water hemlock look like?

Water hemlock is a tall branching plant that can grow three to six feet. It blooms white flowers in June and July with narrow, serrated leaves. Cow and water parsnips are often confused with water hemlock. All parts of water hemlock are poisonous, with the roots being the most toxic and the most palatable.

If you see your dog eating water hemlock, try to induce vomiting and get to a veterinarian immediately. However, since the toxin acts so quickly, prevention is really the key. Learn to identify water hemlock, and don‘t let your dog dig and chew wild plants.

JoAnna Lou

JoAnna Lou

JoAnna Lou is a New York City-based researcher, writer and agility enthusiast.

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