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Are There Certain Types of Plants and Vegetation That Are Toxic to Horses?

Horses benefit from eating a wide variety of plants. Grasses such as timothy, orchard grass, and Kentucky bluegrass often form the base of their diet. Legumes like alfalfa can add some healthy protein and minerals. There are, however, some plants that horses should not eat. An important part of horse ownership is being familiar with these toxic and poisonous plants. That way, you can keep your pastures free of them and prevent your horse from nibbling on them.

The following are some of the most common plants that are toxic or poisonous to horses.


Buttercups are named for their tiny yellow flowers. This plant tends to take over pastures that are over-grazed or sparse. They have a rather bitter flavor, so most horses will not eat them. A few bites of buttercups are unlikely to do much harm, but if your horse grazes on them extensively, they may develop colic or gastric ulcers. 

The best way to keep buttercups at bay is to maintain your pastures well. Practice rotational grazing, and fertilize and reseed your pastures to keep the grass dense and healthy.


Yew is an evergreen plant with short needles and red berries. Your horse is unlikely to encounter yew out in nature. However, some holiday wreaths are made from yew, and there have been instances in which horses have nibbled on yew wreaths that were hung outside their stalls.

Ingesting yew can lead to sudden colic, loss of coordination, and trembling. If you choose to hang wreaths or other greenery in your barn, make sure they are not made from yew.


Pokeweed is a tall, broadleaf plant with red stems. It can resemble a small tree when mature. One of its defining characteristics is its green berries, which appear in bunches.

Pokeweed contains a toxin called phytoloccotixin, which can cause colic and diarrhea. Most horses won’t touch pokeweed, but some may ingest it if pasture is scarce. Luckily, pokeweed plants are fairly easy to spot to dig out of your pasture.

Water Hemlock and Poison Hemlock

Water hemlock, and a closely related species called poison hemlock, are easily identified by their tiny, fluffy, white flowers, which appear at the tips of the plants. Both plants have sparse, tiny leaves and long stems, and they take on a bushy shape. 

Ingesting hemlock can cause neurological symptoms such as nervousness, falling, and lack of coordination. Some horses develop seizures and become aggressive. Hemlock is mostly a concern near ponds and in swampy areas; it doesn’t grow well in dry soil.


Jimsonweed also goes by the names “thorn apple” and “angel’s trumpet.” This plant has one thick stem from which it grows. Its leaves are about the size of your hand and have several lobes; they look similar to oak leaves. When mature, it develops prickly seed pods. 

Jimsonweed has a strong odor, so horses typically avoid it. However, if they do ingest it, jimsonweed can cause a weak pulse, dilated pupils, diarrhea, and sometimes death.


Milkweed is a very common plant. It has a thick central stem and ovular leaves, and if you break the stem or leaves, white liquid will come out. Milkweed actually contains two toxins: one that causes neurological symptoms, and another that causes cardiovascular symptoms. Horses that ingest milkweed often develop colic, appear depressed, become lethargic, and have dilated pupils. Immediate vet care is essential.  Without care, a horse can die within a day of consuming this toxic plant.

Black Walnut

Black walnut trees are incredibly toxic to horses. They do not belong anywhere near your horse pasture. You must also be wary of using black walnut shavings as horse bedding. Even a few shavings of black walnut wood are enough to cause a horse to founder. Exposure is very often deadly. Make sure you source your bedding from an honest, reliable supplier who does not process any black walnut wood on their equipment. 

Bracken Fern

Bracken fern is a species of fern that grows to about three feet tall. Its fronds are soft with rounded edges. Horses do not immediately become ill after eating bracken fern. Rather, its effects accumulate over time. If a horse eats this plant regularly, they’ll develop symptoms such as weight loss, decreased coordination, and lethargy.

Responsible horse ownership involves being aware of these toxic plants and seeking to eliminate them. Thankfully, good pasture management goes a long way toward preventing their growth. 

Another element of responsible horse ownership is consistent training. If you’re looking for resources to help guide and enhance your training, visit Easy Horse Fix. Our educational videos show you how to strengthen your connection with your horse through positive reinforcement.

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