LARIMER COUNTY, Colo. — A warning to pet owners after a poisonous plant kills a dog at Horsetooth Reservoir in Larimer County.

A 3-year-old border collie mix ate a water hemlock on Sunday afternoon and within an hour, the dog was dead.

“It started to go down rapidly with losing all the functions and she passed out,” said Ludi Fischer, a friend of the dog’s owner. “She couldn’t stand up anymore.  She was panting very heavily. Her eyes were out. I mean you couldn’t tell she wasn’t there.”

The dog died en route to the Colorado State University Veterinary Teaching Hospital. A necropsy determined the dog died from consuming a water hemlock plant.

“Water hemlock is one of the most lethal plants in North America,” said Dr. Dawn Duval, Department of Clinical Sciences associate professor at Colorado State University. “It’s a plant that grows in very moist areas, around ditches and lakes.

“This dog just got unlucky and kind of started playfully chewing on a plant that it shouldn’t be chewing. Water hemlock is not a plant that would be particularly appealing to dogs.”

If consumed, symptoms include drooling, muscle twitching and seizures.