by: Jim Freed, WSU Extension Forester
Did you know that there are some native plants and introduced landscape plants that can make livestock very sick and even kill them?
This past winter I had the opportunity to witness just what a landscape tree can do to three cows. I had cut down an old sick horse-chestnut tree last summer. We piled it up on the burn pile but didn’t burn it. I completely forgot about it until we moved our cows into the pasture with the burn pile this winter. As we were moving the cows three of them just fell over and died. We called the veterinarian and after a complete carcass review found no visible reason for the deaths. Since healthy cows do not just die I did a walk about in the pasture where they had been. I saw where there were three spots near the old burn pile where cows had spent the night. On inspection I saw that the old dead leaves on the Horse Chestnut had been eaten as far up as the cows could eat.
I had never heard that horse-chestnut trees were a problem for livestock. I went online and found that my fears were right. The leaves, bark and nuts of horse-chestnut, Ohio buckeye and yellow buckeye, can cause death when eaten in large quantities.
Of the non-ornamental native trees, the most deserving of the skull-and-crossbones warning are those that produce cyanide in their wilted leaves. Cyanide suffocates animals by blocking oxygen transport via the red blood cells. The red maple (Acer rubrum) is one such tree whose leaves are harmless most of the year until wind damage or seasonal change causes them to fall from the tree and wilt. Other trees that are dangerous to livestock are trees in the genus Prunus. This includes cherry, plums, apricots and peaches. These leaves also produce cyanide when wilted, affecting livestock within a few hours of ingestion.
To be safe, remove these deadly trees or relocate livestock away from pastures or paddocks bordered by or containing them. In general, livestock are not likely to eat leaves or any other tree parts unless they are quite hungry. However, when curiosity or boredom spurs exploratory bites, the livestock may ingest enough of the deadlier species to do harm.
So be very careful when you prune landscape plants. Chip and mulch them, pile and burn them, or place them in a location that livestock cannot get access. Care should also be taken when thinning forests that contain wild cherry trees. If you are cutting them down or pruning them, dispose of the brush as soon as possible and keep livestock out of that area until you do.
Some resources to use to see all the native and non-native plants that can kill or sicken livestock are:
So the best rule of thumb is, “if you are not sure if there can be a problem, assume there is, and take the necessary precautions.”