What Plants and Trees Are Toxic To Horses?

15 Common Poisonous Plants For Horses

(Common in the U.S.)

What Plants And Trees Are Toxic To Horses?

There is no perfect pasture, perfect in this case means without toxic plants. Horses can naturally tell good from bad pasture; they have a discerning power. There is no way your horse will go to the bitter pasture when there is sweet and fresh grass around it. While independence is a good thing about horses, it should not make you relax. You are responsible for what your horse eats; you can’t be owning a horse if you don’t love horses. Horse owners are passionate about the grazing and racing lifestyle.

Also, horse riding is about adventure. There is no way you will be familiar with very grass in foreign areas while on a trip. You should not stop to camp anywhere where you think the grass is green and attractive. The unfamiliar plant might also attract your horse but you should know better. You should have an idea of the dangerous plants. You should recognize the name from a distance and keep your horse off. Some toxic levels are too high; one bite can affect your horse.

1. Bracken Fern

Most of the moist places of woodlands in the United States have this plant growing in clumps. The effect of this plant is almost instant. It decreases or stops the absorption of Vitamin B1, which is essential for nervous functions. Ingestion of Bracken Fern often leads to neurological deficiency. Vitamin B1 is responsible for enhancing sensitivity and activity. On ingestion of this toxic plant, a horse depicts signs of depression, blindness, and poor coordination.

The effect is worse on repeated ingestion. First, few leaves might have a mild effect but will still be noticeable. The scariest thing about this plant is a horse can get used to the taste and actually like it. By the time you realize the impact will be huge. However, it is possible to treat the horse, especially if you discover the effects early enough.

2. Hemlock

Hemlock is a wild plant mostly in North America. The plant contains neurotoxins that can cripple your horse’s nervous system. The neurotoxins are spread in leaves, stems, and seeds. Every part of the plant is dangerous. You will notice your horse acting dull or nervous in barely 2 hours. Also, a horse can experience in coordination and extreme tremors and these can lead to extreme health complications if not attended to in the early stages.

Consistent ingestion of the plant leads to depression and heart dysfunctions. The situation worsens to affect the respiratory system, which can easily lead to death. While there is no treatment for this plant effect, animals that ingest small amounts can survive with extra support. 4 pounds is an extremely risky amount for your horse, it can succumb within hours

3. Tansy ragwort

In the countryside of United States, you will come into contact with at least 70 different species of plants. While most of these are pastures, not every plant is fit for your horse. If you are out and about in such places, you better be keen with where you take breaks to avoid exposing your horse to the toxic plants. The irony is horses are easily attracted to toxic and foreign pastures, which are most likely poisonous. While toxic levels vary, the toxicity level in ragwort is scary. The plant affects the liver by preventing cell division. The inhibition process is as a result of pyrrolizidine alkaloids’ presence in the plant.

You will notice your horse has ingested this plant when it exhibits the following symptoms; sudden sensitivity to light, jaundice, loss of appetite, depression, and incoordination. Of course, the effect can be reversed if you notice it early by treating it with natural foods that help revive the liver. From 50 pounds ingestion, the liver damage is considered irreversible.

4. Johnsongrass/Sudan grass

The plant is common in Southern states where it is cultivated as a forage crop. The main component in this plant is cyanide, which is completely harmless. Typically, the grass is ingested alongside other adult plants hence zero negative effect on a horse.

However, cyanide is only harmless when in raw state. Any deformation of its structure as a result of wilting, frost, or any form of damage that can change its chemical compound, makes it toxic. Both Sudan and Johnsongrass have the same chemical compounds and will behave the same when damaged thus high risk to horses. Cyanide inhibits inflow of oxygen hence suffocation. Convulsions, rapid breathing, and gasping are the common symptoms. A veterinary can help if you notice the effect in good time.

5. Locoweed

Locoweed is a common plant both in the West and in South America. The plant contains swainsonine, which has a significant effect on brain cells. Common symptoms of locoism is staggering, body imbalance, awkwardness, and bobbing heads. While there is no specific treatment for the locoweed effect, horses with mild poisoning can recover with close attention of a veterinary. Otherwise, the effects are irreversible.

6. Oleander

The plant is beautiful and most people would use it for landscaping. If you are riding your horse in the hot climatic regions, be keen about this plant. Neriin and Oleandrin are the main chemical compositions in the plant. The toxins affect respiratory systems of a horse; you will notice your horse is breathing rapidly. The irregular heartbeat can also be noticed by tremors and colic.

The toxin travels relatively fast to all parts of the body. However, the effect can be reversed by charcoal if it is noticed early enough. The goal here is to stabilize heart rate. Rapid heart rate can lead to bursting of blood vessels hence death.

7. Red maple trees

Just like with Johnsongrass and Sudan grass, the plant is not of any harm while it is fresh or in its raw form. When the leaves wilt cyanide and other chemicals in the plant become poisonous. The toxin cause breakdown of red blood cells thus compromising on oxygen transfer in the body. The toxins can also inhibit functions of liver among other crucial organs in the body. The toxin is powerful in the sense that only two leaves are enough to risk your horse’s life.

Symptoms of this toxin effect include loss of appetite, rapid heart rate, dehydration, mucus membranes that turn to dark brown gums. Depending on the horse’s metabolic rate, the effect can be evident in an hour or up to 5 hours.

Blood transfusion and IV fluids dosage are the most common treatment methods. However, recovery is dependent on amount of ingestion and how fast you get to the veterinary.

8. Water Hemlock

The plant is common in marshy areas and ditches. While all parts of the plant contain the toxin, the effect is much more on the roots. Consumption of cicutoxin alkaloid paralyzes the central nervous system. While the poison is more in the root, two leaves and a small part of the stem can lead to irreversible effects on your horse. The toxin is powerful and travels fast in a horse’s body.

You can tell if your horse is affected if you notice nervousness, dilated pupils, convulsion, and rapid breathing. Usually, the cardiac muscles get damaged first. The skeletal structure is also likely to be compromised within an hour of ingestion. You can’t miss these symptoms because they are pronounced. A horse is likely to die after ingesting this plant. The few that survive because of quick support care still maintain heart and skeletal muscle for a long time.

9. Yellow Starthistle

The plans are common in Western United States. The toxin targets nervous system and mainly inhibits chewing. There is no treatment for this poison. Usually, effects on the nerve are sustained for a lifetime. Common symptoms for exposure to this poison include clenched facial muscles, improper chewing, and drastic weight loss. The poison is considered chronic and there is little you can do after the first hour of ingestion.

10. Yew

If you live on the West, Central, and Eastern United States, you should be careful about this plant because it is common. It is probably in every pasture in these regions. The plant contains taxine, that lead to respiratory problems. cardiac collapse is a common problem linked to Yew. The effect is reversible if you don’t take quick action. Typically, you should be at a veterinary within minutes of exposure if the horse is to survive. Whether the leaves are raw or dried up, they will still be toxic.

It doesn’t have to be regular feeding on the pasture containing this plant. Two or three leaves of Yew are enough to set your horse on fire. You are likely to find your Horse dead. If you are lucky to find your horse still alive, the heart rate will be low and breathing almost impossible. There is no specific treatment for Yew poisoning yet. Also, the only evident sign of Yew poisoning is sudden death.

11. Black walnut

The trees are cultivated in most parts of the United States. The fruit, stem, leaves, and roots are both harmful. If your horse mistakenly ingests any of the plant components, you might just be losing it within minutes. While there is a treatment for the plant’s poisoning, the poison travels fast and affects cardiac muscles thus stops breathing and other respiratory functions. It is a quick process that most people realize after a sudden death.

The effect of this plants go beyond ingestion. Using wither of the plant components as beddings exposes the horse to itching and the poisonous laminitis. Washing the limbs and feet with cold water can help in reducing the effect. However, if the poison was ingested it is much more difficult to treat

12. Small flower buttercup (Ranunculus abortivus) and tall buttercup (Ranunculus acris)

The plan is commonly found in the central and western part of the United States of America. The effect begins in the mouth immediately the leaves are chewed. The poison, protoanemonin, is released and directly interferes with the digestion process. Typically, a horse reacts to the taste because of the irritating effect of protoanemonin on the gastrointestinal tract.

The effect can be seen in the first hour of ingestion or after two days. The extent of damage depends on the amount of ingestion. Bloody diarrhea, seizures, mouth blisters, colic, tremors, paralysis, and excessive salivation are common symptoms of exposure to this poison

13. Ground Ivy

This is mainly a weed, it can invade any plantation, which makes it more dangerous. It can be in your backyard or field. If your hay contains alfalfa, the horse will experience toxicosis. While other animals are fine after ingestion of this chemical, horses react.

Symptoms include salivation, sweating, pupil dilation, and rapid breathing.

There is no treatment for the alfalfa related attack yet. It can easily be noticed by the purple flower and brown covering.

14. Foxglove

It is common in households as an ornamental plant usually in containers. It is in most places in the United States of America. The risk is death. Ingestion of glycosides also known as cardenolides affects heart functions. The fact that the heart rate is interfered with means blood is not flowing properly to other tissues thus affecting digestion and respiration. The poison concentrations are high in flowers, fruits, and young leaves. However, dry leaves also contain significant amounts of the poison.

15. Acer Spp

There are three different species of Maple tree. Acer is renowned for its significant effect on horses that can easily be identified with clinical signs. It damages red blood cells thus affecting transportation of oxygen.

Toxic plants are not only about taste. It can be enticing to your horse yet the contents are extremely harmful. Also, some plants may have mild effect but on consistent grazing on the field will lead to significant effects on your horse.


I have owned over 50 horses and currently own a small horse farm with 8 horses. I have competed on and off for over 25 years while doing mostly trail riding and cow sorting these days. I write these articles to help anyone out there if you love this article pin it to your Pinterest or Share on other social media platform. Thanks for visiting.

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