extremely poisonous water hemlock
Water hemlock is extremely poisonous & sometimes mistaken for Queen Anne's Lace


There are plenty of poisonous plants out there that we need to keep our pets and animals away from. Some are more poisonous than others, and some aren’t poisonous to all species. There is a plant, however, that is extremely poisonous that will take out just about anything or anyone that ingests it, and that’s water hemlock. Sometimes mistaken for Queen Anne’s Lace, it is considered to be one of the most poisonous plants in North America.

Water Hemlock

This extremely toxic plant can be found near lakes, streams, ponds, canals, rivers or marshy areas all along the water’s edge. The United States Department of Agriculture (USDA) terms water hemlock, or Cicuta douglasii, as it’s also known, as “The most violently toxic plant that grows in North America.” If you have it on your property and you have pets or small children, you might want to rip it out.


And it isn’t just domestic pets that are at risk. Dr. Jennifer Coates wrote that, “Water hemlock contains cicutoxin, tiny amounts of which can have a dramatic, negative effect on the nervous system of animals (including people). All parts of the water hemlock plant are poisonous, but the highest levels of cicutoxin are found in the roots.”  She also noted that poisoning from water hemlock “almost always occurs in grazing animals — cattle, horses, etc.”

Signs of Poisoning

Victims of poisoning from this dangerous plant can present with signs in as little as minutes or up to a few hours. If you think your pets have come into contact with it, seek the advice of a veterinarian immediately, because death can also occur within 15 minutes and 2 hours after clinical signs first appear. The symptoms include drooling, nervousness, muscle twitching, tremors, dilated pupils and rapid breathing.

Border Collie

A few years ago in Colorado, a woman was hiking with her border collie at the Horsetooth Reservoir. Shortly after “playfully chewing” on some plants along the water’s edge the dog fell ill and was dead within the hour. This tragedy was reported by Dr. Dawn Duval, a Department of Clinical Sciences associate professor at Colorado State University, and posted on PetMD.

If you know anyone who routinely walks their pets near conditions the water hemlock plant can be found, or if they might have it on their property, warn them about the dangers associated with it. You never know when it might save a life.