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Farm and Ranch Days: Larkspur concerns addressed

by Wyoming Livestock Roundup

Riverton – It was a crowded room at the Armory in Riverton on Jan. 30 to hear Brandon Greet present the findings of  ahis larkspur control study at the Fremont County Farm and Ranch Days. Greet, a University of Wyoming Extension Educator in Washakie County, researched the affects of four different herbicides on larkspur for his graduate program.

“Larkspur is one of the greatest forages for cattle,” Greet said. “It is the most nutritious and has about 25 percent crude protein in it. It is great forage except that it kills them.”

Dangers of larkspur

“Cattle might accidentally get some larkspur and like the taste. Larkspur has alkaloids in it that are bitter. Cattle actually don’t like the taste of it, but they eat it and think ‘that tasted horrible but it is so good for me,’” explained Greet, “so they eat more of it and begin to selectively eat it.”

The description of Larkspur, Delphinium Glaucum, in a guide to Rocky Mountain wildflowers even mentions that the bluish purple flower is responsible for more cattle losses than any other poisonous plant in the region. 

When cattle overdose on larkspur it causes ataxia and collapse. If they eat enough they suffocate, as it causes respiratory paralysis. The guide continues to say larkspur reproduces from seed, grows from its root crown and one plant can live up to 75 years. 

“Some people are able to prevent cattle from eating larkspur by feeding mineral,” Greet said. “While this has been successful where larkspur is only present in patches, researchers have not been able to prove that minerals cause the larkspur to not effect the cattle when digested or that they do not want to eat it.”

Larkspur does well in drought as it has a large taproot system and is more competitive then other plant species. Greet’s study was completed in 2010 and 2011, and climatic conditions do affect the herbicides’ control. 

Eliminating larkspur

Greet used four herbicides in his two-year study: Streamline, Perspective, Tordon 22K and Escort XP. 

“Based on my research,” Greet explained, “I don’t think Tordon is the go-to herbicide because it only gave me 41 percent control the first year.  Escort gave me 100 percent control the first year. But the second year, they got about the same. Tordon may give you good control, but in both cases Escort will give you better control.”

In the first year of the study, Escort only injured nine percent of the grasses. Escort does lower the biomass slightly, but Greet is not sure that will happen every time. Tordon actually helped increase the biomass, but saw 15 percent grass injury. Part of this is that Tordon causes some yellowing, but the plants continue to grow fine.

“Personally, if I’m not exterminating things, I can handle some injury to plant forbes,” Greet said.  “You will reduce your species richness with the smaller annual forbes being hurt by the herbicide. The annuals should come back in the following year from the seed bank. The perennial grasses did not seem to be affected.”

Greet’s study was located between Kaycee and Ten Sleep where larkspur is the prevalent forage. In low water years, larkspur is taller than the grasses, and, as cattle are side feeders, they tend to graze it more.

Research shows that if larkspur is controlled, you can figure on having 10 years of larkspur free pasture. Even if the larkspur regrows the next year, it takes the long-lived perennial 10 years to become a mature plant. Greet said he would argue with that research, and thinks that it is more correct to count on five years of control as the leafy plant will be present just not blooming. Greet urged the audience to check with their weed and pest district as some cost share for larkspur control.

Grazing impacts

In early spring larkspur is the most bitter and the most toxic, but cattle seem to not want to graze it. In late summer after it blooms and begins to dry out, the plant is more palatable and cattle will graze it more readily. The alkaloids are stored in the roots in the winter and released into the plant and leaves in the summer.

If cattle consume 20 milligrams per kilogram of body weight, larkspur will cause ataxia and collapse. They need a little bit more than that to make it so that they cannot breathe. 

“We’ve found cattle on their backs in the bottom of a draw,” Greet said. “We expect they were eating larkspur, collapsed on the side of hill and rolled down. Larkspur can kill in a number of ways.”

Sheep will graze larkspur, though it takes quite a bit to kill them. There is not quite the same death loss with them as in cattle. Greet said that the wild horses that run in his area do not seem to help in the control of larkspur and also don’t seem to be affected by it.


Treatment myths abound for the overeating of larkspur, and include turpentine, bacon fat, whiskey, chewing tobacco and bleeding the animal from the tail vein. Greet said that when bleeding has been successful most often the animal hadn’t eaten that much larkspur. He has come across research that seems to support the chewing tobacco treatment, though.

“There is question on whether the currently available drugs, Physostigmine and Neostigmine, actually work for livestock,” Greet said. “The treated animals might not be severely affected by larkspur. In some cases treating the cattle like you would for bloat has been successful.”

Greet took one last question before closing his presentation: Is the delphinium that grows in my wife’s yard the same thing as larkspur? 

“Yes it is, so I wouldn’t let your cows graze in the yard,” replied Greet. 

The questioner responded, “I wouldn’t let that happen. I like to eat supper.”

Melissa Hemken is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to

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