Horse Illustrated Magazine

Horses are usually content to simply graze on the grasses that you want them to, but there are some poisonous plants out in the world that are bad for horses—and there are some curious horses who like to nibble on odd plants. To that end, here are 10 plants that are toxic to horses that you’ll want to watch out for.

1. Buttercup

Buttercups are wonderful wildflowers to behold—during the spring months they will fill up a meadow with their brilliant but small yellow blossoms. The problem is that some of the natural chemicals in buttercups have a nasty habit of interacting with each other in an unpleasant way if the plant is crushed—like if a horse chews on it. Because of its bad taste, most horses will avoid the plant if possible, but if they do consume it, buttercups can cause mouth and digestive irritation. Common to moist pastures (particularly those near wooded areas), buttercups can be deterred by regular mowing and by not allowing the pasture to be overgrazed.

2. Milkweed

Some people like having milkweed around because it helps Monarch butterflies, which only lay their eggs on this specific plant (since caterpillars use it as a food source before going into their cocoon). Doing Monarch butterflies a favor is good, but you also need to do your horses a favor and make sure that there is no milkweed in their pasture or anywhere they might be able to access it. Native to most of the U.S. except the Southwest, milkweed contains a milky substance containing galitoxin and cardenolides that are poisonous even in small amounts. Dried milkweed should be avoided in hay, too.

3. Bracken Ferns

When wooded areas are cleared to create horse pastures, the property sometimes “wants” to become woods again. In locations like this, bracken ferns commonly encroach around the edges of the pastures, and if the pasture is overgrazed, horses might attempt to eat these ferns. It takes a large amount to cause toxicity, but bracken ferns can cause a vitamin B1 deficiency in horses, leading to neurological symptoms. There are a few different species of bracken ferns, and overall they can be found almost everywhere in the U.S.

4. Jimsonweed

A tall plant that can reach heights of five feet, jimsonweed contains two tropane alkaloids that can affect the nervous system and cause a variety of symptoms, including colic, increased pulse and respiration, and thirst. Happily, horses generally dislike the taste and will probably leave the plant alone as long as the pasture is healthy otherwise. Jimsonweed is native to most of the U.S.

5. Foxgloves

Foxglove flowers are cultivated in gardens, but also grow wild in the northwestern U.S. An attractive addition to any landscape and useful in the production of heart medications, foxgloves are nonetheless poisonous to horses (as well as other animals and humans), with consumption leading to serious cardiac issues. It’s well worth the effort to make sure your horse cannot come into contact with these poisonous flowers.

6. Tomatoes/Potatoes (nightshade family)

Those tomatoes and potatoes in your garden might be tasty for you, but it’s best to keep these plants away from your horses. The foliage of these nightshade plants contain solanine and other chemicals that can cause depression, low heart and respiratory rates, and colic in horses. The same goes for the raw tuber (edible) portion of potatoes. As far the fruit of tomatoes, you might find a mixed bag of recommendations as to whether horses can safely consume them. Since there are so many other safe treats for your horse, it’s probably wise to skip tomatoes altogether.

7. Pokeweed

Despite being a weed, and despite being highly poisonous, pokeweed—also called “poke salad”—has a history of usefulness in the U.S. The berries have been used to make dye, and with proper knowledge and preparation, the immature leaves and shoots have been used for food. Nevertheless, pokeweed is highly toxic to humans and horses, so this is definitely a plant that should be eradicated from your pastures. All portions of the plant contain toxins (especially the seeds and roots), which become stronger as the plant ages. Horses that consume large amounts of pokeweed may suffer from colic, weakness, or convulsions; it’s also irritating to the skin. Pokeweed, which grows throughout the spring and summer, is common throughout the eastern U.S. and portions of the west coast.

8. Rhododendron

This is a good one to watch out for since it’s commonly cultivated around homes and in landscaping. Rhododendrons are flowering shrubs that contain grayanotoxins (as do azaleas, laurels, mountain pieris, and fetterbush), which can cause severe digestive and cardiac problems in horses that consume a lot of it. Because it’s a cultivated plant, you’ll find it widespread throughout the Northern Hemisphere, blooming in spring and summer, although it remains poisonous throughout the year.

9. Water Hemlock

Found throughout the U.S. in low, wet areas, water hemlock—particularly the root—is quite poisonous to horses (and humans). Ingestion quickly affects the nervous system, causing general agitation and convulsions; if enough of the plant is consumed, it can lead to respiratory paralysis. If prevalent in your area, you might consider fencing off low areas of your property.

10. Tansy Ragwort

Tansy ragwort causes liver damage to horses that consume it, so it’s definitely not a plant to take lightly. The weed is native to Europe and Asia, but now grows wild in the U.S. in New England, the northwest, and parts of the midwest, where it tends to grow in sandy, moist areas.

While these are just 10 common plants that are bad for horses, there are many other toxic plants to watch out for. it’s important to know what plants are toxic to horses.

What are some of the common ones in your area? Have you ever had a horse have to deal with toxicity?

Further Reading

• Poisonous Plants to Horses from the University of Tennessee