White snakeroot: a toxic plant to horses

  • Don’t allow your horse to eat white snakeroot. Horses may die one to two days after eating white snakeroot.

  • White snakeroot has smooth upright stems, tooth-edged leaves and white flower clusters.

  • White snakeroot grows in shady areas and woodlands.

  • Applying multiple rounds of herbicide, fencing horses out and mowing are the best control practices.

Identifying

  • One to three feet tall

  • Stems are smooth, upright and branched at the top

  • Leaves have toothed edges and taper to a pointed end

  • Small white flowers arranged in clusters

White snakeroot is a perennial.

White snakeroot plants
Flowering white snakeroot plants
Mature white snakeroot plant
Mature white snakeroot plant
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Toxicity

An oil extract in the white snakeroot makes the plant toxic to horses. The plant’s oil extract content declines slowly as it dries. But poisoning can still occur in horses that eat white snakeroot in hay or as dry plant stalks. White snakeroot is also toxic when horses eat it fresh.

There are no reports for the exact toxicity levels for horses. But horses are generally believed to be more prone to white snakeroot than ruminant livestock. Toxicity in cattle occurs after they eat 5 to 10 percent of their bodyweight over a few days.

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Control

  • Don’t allow your horses to graze this plant under any circumstance.

  • Fence off wooded areas.

  • Provide supplemental feed to horses on pasture (especially in the late fall or during dry conditions).

  • Be aware that a single application of herbicide won’t control white snakeroot. You will need to apply a herbicide multiple times.

Fencing horses out, mowing and applying herbicides multiple times may be the best control options. Always carefully follow information on herbicide labels, including grazing restrictions.

Krishona Martinson, equine Extension specialist; Lynn Hovda, DVM, adjunct assistant professor, College of Veterinary Medicine; and Mike Murphy, DVM, former professor, College of Veterinary Medicine 

Reviewed in 2018

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