Water Hemlock: Dangerous Plants for Dogs · The Wildest

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Water Hemlock Poisoning in Dogs

Pet parents, watch out for a common — but deadly — plant.

by JoAnna Lou and Dr. Bartley Harrison, DVM
Updated September 19, 2023
dog playing in a pond
Photo: Rafael Shiga / Unsplash
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There’s no way around it: Water hemlock is a highly toxic plant that can be fatal to dogs. The entire plant is poisonous, but the roots are the most toxic part. Symptoms of poisoning can appear within minutes to hours of ingestion and can include vomiting, diarrhea, excessive salivation, seizures, coma, and death. If you think your dog has ingested water hemlock, seek veterinary attention immediately. Early treatment can increase the chances of survival.

There are very few reports of water hemlock poisoning dogs, so not much is known about how much plant material is needed to cause symptoms. As little as half an ounce of water hemlock tuber (root) has been found in the stomach of a full-grown cow who died of water hemlock poisoning. It would probably not take much at all to cause severe symptoms in dogs.

What is water hemlock toxicity?

Water hemlock is highly toxic to bothpeople and pets. The plant contains the poisonous chemicalcicutoxin, which has a carrot-like odor and affects the brain and central nervous system if ingested. Just a few bites of water hemlock can kill a dog within hours, making it one of the most lethal plants on this continent.

Some animals have even been poisoned from drinking water that has been contaminated with trampled water hemlock roots. The plant grows near bodies of water, such as rivers and lakes, and areas where water collects, like ditches.

If water hemlock is consumed,symptoms can beginwithin 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 a dog, there is a chance at recovery, but there may be temporary or permanent damage to the heart or brain.

What does water hemlock look like?

Water hemlock is a tall, branching plant that can grow three to six feet in height. It blooms with white flowers in June and July and has 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.

What are the different types of water hemlock?

Four different types of water hemlock have been recognized. These different species are all very similar in appearance and in toxicity. They all grow in very moist soil, most commonly along streambanks, in marshy areas, or in wet meadows. Water hemlock plants in general have a variety of common names, including poison parsnip, wild carrot, wild parsnip, false parsley, and beaver poison.

The common names of specific species give some clues to the minor differences in appearance and growing region that separate them:

  • Cicuta virosa: northern water hemlock, cowbane, Mackenzie’s water hemlock

  • Cicuta maculata: spotted water hemlock, spotted parsley, spotted cowbane

  • Cicuta bulbifera: bulbous water hemlock, bulblet-bearing water hemlock

  • Cicuta douglasii: western water hemlock, Douglas water hemlock

Water hemlock is particularly dangerous because its appearance is similar to many edible plants, including water parsnip, wild carrot, wild parsnip, celery, and wild celery. Never assume that a wild plant is safe for your dog to eat based on appearance alone.

Symptoms of water hemlock poisoning in dogs

  • Nervousness

  • Abdominal pain

  • Excessive salivation and frothing

  • Muscle twitching

  • Pupil dilation

  • Rapid pulse

  • Slow breathing

  • Tremors

  • Violent convulsions, grand mal seizures

  • Death

How is water hemlock poisoning diagnosed?

The diagnosis of water hemlock poisoning in dogs is made based on identification of plant material. If you see your dog eating a plant that looks like water hemlock, carefully package up any plant material, and bring it to the vet with your dog as soon as possible.

In dogs that are showing symptoms of water hemlock toxicity, examination of the contents of their stomach after vomiting or gastric lavage could show the presence of suspicious plant matter. Unfortunately, water hemlock poisoning is often diagnosed after death in animals because of the severity of the toxicity and the rapid onset of symptoms.

What are the treatment options for water hemlock poisoning in dogs?

In cases of known ingestion, water hemlock poisoning treatment must be started quickly. Decontamination should be performed as soon as possible. In dogs that are conscious and not showing signs of incoordination or sedation, vomiting may be induced to get some plant material out of the stomach.

Vomiting does not empty the stomach completely, though. Water hemlock is deadly enough in small quantities that gastric lavage under anesthesia would likely be recommended to rinse the stomach out completely.

Medications to help with nausea and pain from cramping may be administered. If symptoms progress and convulsions begin, seizure control is vital. Severely affected dogs may need to be placed on a ventilator to support their breathing.  Due to the rarity of water hemlock toxicity, consultation with an animal poison control center is key. Even with early intervention and aggressive care, water hemlock can be fatal.

FAQs (People also ask):

Can water hemlock poisoning be prevented?

The best ways to prevent water hemlock poisoning are to learn the appearance of toxic plants like water hemlock, keep your dog away from unknown plants, and teach a “drop it” command to make your dog release something they’re chewing on.

Can water hemlock poisoning be treated at home?

Water hemlock poisoning is rapidly fatal and cannot be treated at home. Even with rapid veterinary intervention, this plant can be deadly in small quantities. See a veterinarian as soon as possible if you suspect your dog has eaten water hemlock.

Is there an antidote for water hemlock poisoning?

There is no antidote for water hemlock poisoning. Care for water hemlock poisoning involves getting all the plant material out of the dog’s stomach and providing supportive care for seizures, slowed breathing, and other problems caused by the toxin.


JoAnna Lou

JoAnna Lou

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

Dr. Bartley Harrison holding his dog

Dr. Bartley Harrison, DVM

Dr. Bartley Harrison, DVM is a small animal veterinarian based in North Carolina who has practiced emergency medicine since graduating from the Texas A&M College of Veterinary Medicine. His primary interest areas include pain management, cardiology, and the treatment of shock.

He is a member of the Veterinary Emergency and Critical Care Society, American Veterinary Medical Association, and American Medical Writers Association. In addition to his clinical work, he writes pet health articles to help provide accurate information for both new and experienced pet parents. When he’s not working, he enjoys cooking, traveling, reading, and going on adventures with his dog.

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