Posted: Thursday, July 07, 2011 12:00 PM
Carol Ryan Dumas/Capital Press
Michael Ottley, with the Twin Falls County Bureau of Noxious Weed Control, wears gloves when handling poison hemlock along Rock Creek. The plant can be lethal to animals and humans.
Poison hemlock can cause abortions, crooked calf
Poison hemlock is found in almost every county in Idaho. That can mean big trouble for humans and livestock.
"It's one of the most toxic plants in the Western Hemisphere," said Roger Batt, coordinator of Idaho Weed Awareness Campaign. "It is so toxic that horses and cows literally can die within hours after eating this poisonous plant."
Its been a problem for Charlie Lyons, Idaho Cattle Association president, who ranches northeast of Mountain Home.
"We've lost cattle -- not in quite a while," he said. "We learned some lessons."
He's seen cattle eat the stalks of the plant in the spring, and it doesn't seem to bother them. But he's had trouble in the fall, usually after a hard frost, he said.
"The roots are deadly," he said.
Either something makes the plant more palatable in the fall or the water table goes down, making it easier for cattle to access the root, he surmised.
His strategy is to spray the areas he plans to graze in the fall with a herbicide before the plant flowers.
Lyons might just have been lucky in his experience with the weed, experts say.
While the greatest concentration of toxin is in the root area, the entire plant is toxic, said Batt and Mike Ottley, of the Twin Falls County Weed Bureau.
While Lyons said it only takes a small chunk of the root to kill livestock, any part of the plant can kill an animal if it eats enough, Ottley said.
"Cattle like it because it has a salt content in it. They get a taste for it and keep eating," he said. "All of it's poisonous, but they'll eat it down to the ground."
If pregnant cows eat less than a lethal amount it can cause abortion or a calf abnormality called crooked calf, he said.
Poison hemlock grows in riparian areas, along stream banks, canals and ditch banks, with no discrimination between city and country. It grows for two years, flowers, seeds and dies.
In its first year, it's low to the ground and the grasses livestock graze on are taller, Batt said. But now it is at the flowering stage, white flowers on 6- to 8-foot purple-mottled stalks.
The weed has been mistaken for wild parsley, dill or fennel. The root has been mistaken for parsnip and its root and seeds for wild carrots or anise, he said.
It's an easy plant to kill, either by pulling it out with rubber gloves or spraying with a herbicide registered for use on the plant, he said.
More information, photos and video can be found at: www.idahoweedawareness.org
Poison hemlock and other noxious weeds can be reported by calling 866-439-3337.