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"Poisonous" does not mean deadly. Some manifestations of toxicity are subtle. The dose, as always, determines if a plant is safe source of nutrients or a toxic hazard.

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BRIEF: Are buttercups dangerous to horses?

My question concerns buttercups. I have been told that these are harmful to horses, and I have a great deal of the creeping variety that has shown up in my pastures this year, while my horses have been away. Can you confirm that these are indeed dangerous and if so, what can I do? Would mowing them be sufficient?


It can be a real pain, literally, to your horse. The protoanemonin causes a mustard-gas like effect, blistering the lips and mouth and, if ingested, causes severe GI disturbances. (I don't mean it releases a gas, it doesn't, but the blisters look a little like mild mustard chemical burns) Fortunately, it is so irritating that most animals don't eat enough to get sick. If this makes up enough of your pasture that you think this might become a problem, then you need to consult some weed control experts at your location to see how to reduce the amount of Rannuculus in the pasture. I don't have an exact dose, but if by "a great deal" you mean the horses have nothing else to eat, then at least mowing and overseeding with the appropriate forage grasses might be worth it.