Black Walnut Tree Shavings as Trail Mulch?

Q: This summer we are planning to start making riding trails on our heavily wooded property. As we cut down the branches and trees, we plan to chip the wood to mulch the trails. However, we have a good number of black walnut trees, and I am wondering if the wood chips pose a health risk to our horses.


A:Black walnut shavings and wood chips contain the toxin juglone that is suspected to be a principal agent in causing laminitis. This is a problem to horses if they contact or eat the shavings. However, the toxicity apparently only occurs if the black walnut shavings are fresh. If they are well seasoned, then the toxicity is negligible. I would assume that if the chips were spread on the trail and allowed to weather for a month or more, then there would be little risk to horses using the trail.

Bedding the horses on black walnut shavings is more likely to be a problem because of the greater contact and exposure.

For more information on black walnut toxicity, see

About the Author

Anthony Knight, BVSc, MS, Dipl. ACVIM

Anthony P. Knight, BVSc, MS, Dipl. ACVIM, is a professor of large animal medicine in the College of Veterinary Medicine and Biomedical Sciences at Colorado State University. He received his veterinary degree from the University of Nairobi, Kenya, in 1968. After completing a master’s degree at Colorado State University, he joined the faculty in 1974. His current professional interests include livestock heath, foreign animal diseases, emergency management, and plant toxicology. He has written two books on poisonous plants of animals in North America, and maintains a poisonous plants website for use by anyone wanting poisonous plant information.

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