Harmful Flora for Horses: Identifying and Avoiding Common Toxic Plants

Horses are natural grazers and spend plenty of time eating plants. However, not all plants are safe for horses to consume. In fact, some common flora can be highly toxic and even deadly if ingested. In this blog post, we'll explore some common harmful plants for horses and how to identify and avoid them!

Red maple

Red maple trees are common in North America and are highly toxic to horses. The leaves, bark, and twigs contain a toxin called gallic acid, which can cause severe anemia, colic, and other symptoms in horses. Red maples are most toxic when the leaves are wilted or dried in the fall.

Black Walnut

Black walnut trees are also common in North America and can harm equines. The leaves, nuts, and bark contain a toxin called juglone, which can cause laminitis, colic, and other symptoms. Black walnut shavings are also toxic and should not be used as horse bedding.

poison hemlock plant

Poison hemlock

Poison hemlock is a highly toxic plant found in many regions of the world. All parts of the plant are poisonous, and even a tiny amount can cause respiratory failure and even death in horses. Poison hemlock is most frequently found in pastures and along roadsides.


Nightshade plants, such as deadly nightshade and horse nettle, contain toxic alkaloids that can cause a range of symptoms in horses, including colic, diarrhea, and respiratory distress. Nightshade plants can be found in multiple regions of the world and are most commonly found in pastures and along fence lines.


Buttercups are prevalent in numerous world regions and can be toxic to horses if ingested in sizable quantities. The toxin in buttercups can cause blistering in the mouth and digestive tract, leading to colic, diarrhea, and other symptoms.


Yew is a popular landscaping plant that is highly toxic to horses. The entire plant, including the leaves, stems, and seeds, contains a toxin called taxine, which can cause cardiac arrest and death.

bracken fern

Bracken Fern

Bracken fern is a common plant in a significant number of regions around the world and can be toxic if consumed in big doses. The toxin in bracken fern can cause thiamine deficiency, leading to neurological symptoms and death.


Rhododendron is a popular ornamental plant that can be toxic to horses if they digest substantial amounts. The toxin in rhododendron can cause gastrointestinal upset, difficulty breathing, and death.


Jimsonweed is a prevalent plant in many regions worldwide and can be toxic to horses if ingested in vast portions. The toxin in jimsonweed can cause various symptoms in horses, including colic, respiratory distress, and even comas.

wild cherry

Wild Cherry

Wild cherry trees grow in many regions of the world and can be toxic to horses if eaten in large quantities, like a few other florae. Wild cherry toxins can cause respiratory distress, colic, and other symptoms.

It's important to remember that this list is not exhaustive, and many other plants can harm horses. If you suspect your horse has swallowed a toxic plant, seek veterinary attention immediately.

Here are some tips for identifying and avoiding harmful flora for horses:

  1. Know your plants. Take the time to learn about the common plants in your area and their toxicity levels. Keep a list of toxic plants handy to quickly identify and remove them from your horse's environment.
  2. Inspect pastures and grazing areas regularly. Walk through your pastures and grazing areas regularly to check for toxic plants. Remove any plants you find immediately.
  3. Monitor your equine’s grazing behavior. Keep an eye on your horse while grazing, and ensure they are not eating anything they shouldn't be. If you notice your horse eating a plant you're unsure about, remove it immediately.
  4. Provide plenty of forage. Ensure your horse has access to plenty of safe forage at all times. Horses that are hungry or don't have enough forage available may be more likely to eat toxic plants. 
  5. Keep pastures and grazing areas well-maintained. Regularly mow and remove weeds from fields and grazing areas to prevent toxic plants from taking over.
horse with face in a flower field

The best way to avoid harmful flora for horses is to know what plants are safe and which are toxic. Take the time to familiarize yourself with the common plants in your area and learn how to identify them. If you're unsure whether a plant is safe for your horse to eat, it's best to err on the side of caution and remove it from your horse's environment. You can also consult a veterinarian or equine nutritionist for advice on what plants are safe to feed your horse.

Learn about the common toxic plants in your area, monitor your horse's grazing behavior, and keep their environment well-maintained. By following these simple tips, you can help keep your horse safe from harmful flora and ensure they stay healthy and happy. To get your horse back to peak health, Equine Medical & Surgical Associates is here to help! See how some of our products, like Health-E, can help with neurological issues, or Heave Ho can assist with breathing and respiratory problems. These products and others can aid in your equine's health issues. If you have any questions about your horse's health or would like a consultation, feel free to email Dr. Reilly at equinemedsurg@equinemedsurg.com