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Toxic Plants

     Toxic Plants can have deadly effects on horses. While most horses won't browse on them, if kept on dry lots or left with little to eat, bored or starved horses may eat things they normally wouldn't. Some plants merely cause an inconvenient side effect such as hives or photo-sensitivity, but others can easily cause laminitis or colic in small quantities, or even death. There are many plants that you would actually consider "safe" that can have harmful effects, such as brome grass or fescue that both are linked strongly with laminitis. But for the sake of this article, we will focuse on plants horses would not normally eat and cause immediate and severe reactions. This cannot be a comprehensive article, but I wanted to point out some trees and plants that really are better left out of the pasture to avoid potentially devastating side-effects.

This month's focus: Toxic Trees


Toxic Trees

Toxic trees can have varying effects. Ones to look out for are Wild Cherry, Black Walnut, and Kentucky Coffee Trees. Wild Cherry branches if broken, such as in a storm, the leaves become toxic with cyanide as they dry out. Naturally shed leaves in the fall do not have the same effect, but better to avoid them altogether. Black Walnut is so toxic that simple contact with shavings made from the wood can cause SEVERE acute laminitis. Kentucky Coffee Trees produce seed pods that when eaten by livestock, give the animals what is essentially like nicotine poisoning and death is likely. Other trees can also be bad, such as Oak trees producing acorns that can also cause laminitis and colic. I've known horses to be housed in pastures full of Black Walnuts and Oaks that never suffered any harm, but some horses are not that choosy or seem to love the taste of acorns and will gorge on them and need to be fenced off seasonally.

   Cherry Trees: They range from shrub sized up to 30 feet high. They have reddish brown bark and obviously produce Cherries. The leaves are typically 2-6 inches long with a toothed edge and pale to dark green, changing each fall before shedding, to a range of different colors.  While the focus is more on wild cherries, I would recommend not planting ANY type of Cherry where the branches may dead fall or be accessable to horses. Cherry trees grow pretty much everywhere in the USA.

   Black Walnut: This type of hickory tree grows all over forested areas and is frequently cultivated for the nuts and wood. It can be quite large and has rough bark. The leaves grow on stems with multiple small leaves per stem. The nuts start to appear through the season and fall in the autumn. The tree is quite hardy and long lived. I saw far more in Arkansas/Missouri than in Kansas.

Coffee Tree: The seeds were previously used to produce a type of coffee, but the seeds are quite hard and need to be heated to neutralize the toxins. The Seed Pods appear most visible in the winter when the leaves have fallen. The Pods remain in the top until spring. The pods resemble giant pea pods with hard seeds inside. This is the part that is toxic to animals, the pod and its contents. I don't recall ever seeing them in the Ozarks, but I wasn't aware of the tree at all until recently. It is considered fairly uncommon but is sometimes part of old homesteads or was used in landscaping.

Oak Trees: They come in a wide variety. One noteable thing about oaks are that the acorns are the only really harmful part, and the tanic acid is easily removed with a good soaking rain, at least until the next batch fall to the ground. Native Americans used to eat them after soaking in water to remove the tannin and other than the law of avoiding over-indulgence of any one food, acorns are not particularly dangerous after a good rain. Just watch the greedy horses and keep them off the acorns if you have a "bumper crop" until it rains.

Next month: Shrubs and weeds.


Illustration of Wild Cherry Tree
Illustration of Black Walnut Tree
Photo of Coffee Tree with Pods in Winter
Coffee Tree Seed Pod and Seeds