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Pine Ridge Equine Hospital

Plants to Avoid Having in Your Horse Pasture

Horse Standing in Field near Tree

Turning out your horses offers many benefits. When your horses spend the day in a pasture, they're likely to be healthier and stronger, thanks in part to the many nutrients in forage.

Turnout can even reduce the risk of colic, chronic obstructive pulmonary disease (COPD), and behavioral issues, according to Kentucky Equine Research. Unfortunately, some of the plants found in pastures could sicken or kill horses. Removing these dangerous plants will help you protect your horse's health.

  • Hemlock.

Spotted or poison hemlock contains clusters of small white flowers on spindly stems. Eating hemlock can cause colic, shaking, coordination problems, and decreased breathing and heart rates. Consuming just a few pounds of hemlock could kill your horse.

  • Red Maple Leaves.

Although fresh red maple leaves probably won't bother your horse, eating wilted or fallen leaves might cause serious illness or death. According to Equus, eating one or two pounds of the leaves could be fatal for horses. Be sure to check your pasture regularly for fallen branches to decrease the risk. Poisoning symptoms include rapid heart rate, fast breathing, lethargy, disinterest in food, pale or yellow gums, and black or reddish-brown urine.

  • Pokeweed.

Pokeweed is particularly common around fences and can vary in height from 4 to 10 feet. The plant has large leaves and purple berries. Eating the roots, stems, or leaves of the pokeweed plant can cause diarrhea, colic, and burning in the mouth.

  • Japanese Yew.

Japanese Yew shrubs can grow up to 30 feet tall and feature spiny needles and red berries. Just one mouthful of Japanese Yew can kill a horse in as little as 30 minutes, according to Rutgers: New Jersey Agricultural Experiment Station. Horses that eat the needles or berries of the yew shrub die from cardiac or respiratory failure.

  • Black Walnut.

Every part of the black walnut tree is toxic, including the roots, bark, wood, nuts, and shavings. If your horse is sickened, it may develop lower limb swelling, laminitis, increased temperature and pulse rate, heavy breathing, lethargy, and depression.

  • Rhododendron, Azalea, and Mountain Laurel.

All of these flowering plants contain grayanotoxins, which can cause muscle tremors, drooling, coordination issues, colic, diarrhea, abnormal heart rate, and even death.

  • Tansy Ragwort.

Tansy ragwort plants grow from 2 to 4 feet tall and feature clusters of yellow flowers and leaves with ragged edges. Eating the plant causes irreversible liver damage in horses. Symptoms can include loss of appetite, sensitivity to light, disinterest in food, jaundice, and coordination problems.

  • Johnsongrass.

Both Johnsongrass and Sudan grass produce a cyanide compound that makes it hard for your horse to absorb oxygen. Eating healthy adult plants probably won't hurt horses, according to Equus. Curing these grasses for hay also won't cause problems. Cyanide is released when the leaves wilt, are trampled, or are exposed to frost. Symptoms include rapid breathing, frequent urination, and defecation, convulsions, gasping for breath, and shaking.

  • Nightshade.

Any of the plants in the nightshade family can cause a toxic reaction in horses, including bittersweet and black nightshade, horsenettle, potatoes, and tomatoes. If horses eat the leaves or shoots of the plants, they may develop loss of appetite, diarrhea, dilated pupils, loss of appetite, coordination problems, convulsions, and hallucinations.

  • Other Plants.

Other plants that could sicken your horse include buttercups, Alsike clover, bracken fern, jimsonweed, milkweed, yellow sweet clover, English ivy, locoweed, and wild cherry trees.

Luckily, horses don't like the taste of many of these toxic plants and will only resort to eating them if there's not enough forage in the pasture. Removing toxic plants and checking the amount of forage available can help reduce the risk of poisoning.


Kentucky Equine Research: Grazing Benefits Horses and Mangers, 10/9/14

Rutgers: New Jersey Agricultural Experiment Station: Poisonous Weeds in Horse Pastures

Equus: 10 Most Poisonous Plants for Horses, 4/11/05

UF/IFAS Extension: Dangerous Plants to Horses in Paddocks and Small Pastures