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Top 15 Plants Toxic to Horses Lurking in Your Pasture

Written by Rachael Kraft (Updated April 20 2023) 

Is your beautiful green pasture actually a field of plants toxic to horses? Like it or not, there are a lot of dangerous plants out there that could cause serious harm – or even death – for your horse. That’s why it’s important for you to understand and be able to identify the top criminals of the plant world lurking in your pastures.

In this article, we’re going to take a look at the worst of the worst. We’ll explain why each plant is so dangerous and share some ideas for how you can protect your horses from danger. The act of poisoning should be left to spy movies and action thrillers. It has no place on your farm!

Without further ado, here are the top 15 poisonous plants to horses lurking in your pastures:

#1: Bracken Fern

bracken fern

Most plants toxic to horses taste gross to them, but not this one!

Some horses actually love to eat the bracken fern, so it’s a good one to know right from the start. This perennial fern tends to grow in clumps in moist open areas and woodlands.  Leaves can reach heights of two or three feet.

Your horse would actually need to eat hundreds of pounds of it to start experiencing ill effects. But that’s not out of the question if your horse has access to the plant and enjoys the flavor. That’s why you need to keep it out of your pastures.

After eating too much of this plant, horses will experience vitamin B1 deficiency which leads to neural dysfunctions. This shows up as depression, incoordination, and even blindness.  Your vet will likely prescribe large doses of thiamine over the course of one or two weeks to help your horse recover.

#2. Clovers


The rabbit from the movie Bambi sure enjoyed eating clovers, but your horses should stay away as clover is among the top plants toxic to horses. There are several kinds out there, but alsike covers cause horses to experience blistering on their light colored skin (photosensitivity) and liver disease.

Red and white clover, which looks very similar, can also be a problem for horses. The plants themselves aren’t a problem, but they are often infected with a black patch fungus which can cause excessive drooling known as the “slobbers!”

Your best defense is to watch your pastures for either of these plant types and try to promote the growth of grass instead.

#3. Deadly Nightshade


Do you watch what’s in your horse’s hay for toxic plants growing as well? Well, you should.  

That’s because deadly nightshade can accidentally be mixed in during the baling process. This poisonous plant to horses is related to the pepper plant and is most often eaten after being accidentally baled into your horse’s hay. 

It grows best in sandy soil and dry conditions and has a bell-shaped purple flower and small, round fruits. After being eaten, symptoms will include colic, loss of muscle control, neurological signs, dilated pupils and even death.

#4. Box Elder Maple