Plants Toxic to Horses

You must be aware that horses can eat certain plants if you have a garden. These weeds, as well as plants and shrubs, can be harmful to horses or ponies. To keep your horses safe, learn how to identify these plants in your yards and pastures.

Deadly Nightshade

Deadly nightshade is able to thrive in even dry conditions. The small, oval-shaped, purple flowers are reminiscent of a black currant. The fruit is a deep, shiny, black/purple color. This plant is toxic to pets and humans. It is also quite dangerous because the fruit is sweet.

Its leaves are dark green, smooth-textured, and resemble a tomato plant. It is part of the same family as pepper, tomato, and potato plants.

Horses may accidentally ingest toxic plants that have been bailed into the hay. 1

  • Colic-like symptoms
  • Loss of muscle control and inability to rise
  • Disorientation, stumbling, and other neurological signs
  • Dilated pupils
  • Death (if consumed in sufficient quantities)


The flowers are cup-shaped and yellow, while the leaves have sharply lobed foliage. Buttercup plants can be well grazed. Horses will avoid buttercups if there is more desirable food. This is because of their bitter taste and tendency to blister the mouth. Buttercups can be safely eaten after a hard freeze or when dried in hay.

Buttercups may cause:1

  • Drooling and irritation around the mouth, such as blisters or inflammation
  • Colic-like symptoms
  • diarrhea

Bracken Fern

Bracken ferns can be found in many places, including along roadsides, fields, light bushy areas, and gardens. The ‘fiddleheads,’ which are triangular fronds, become unfurled in the spring. Even though bracken fern is toxic, it can be dried and rolled into hay. Horses can become vitamin B1 deficient if they eat large amounts of this fern.

1 These are some symptoms of bracken fern poisoning.

  • weight loss
  • Weakness
  • gait abnormalities
  • An abnormal heartbeat and/or rhythm
  • Inability to Rise
  • Death

Horse Tails

These soils, which are mainly made of sand or gravel, drain quickly and are ideal for this horsetail. Some varieties can grow in areas that are wetter. The plant is toxic whether it is dried and made into hay or eaten fresh. This plant’s toxin can cause the horse to lose vitamin B1 (thiamin) in its gastrointestinal tract.

2 are the symptoms of horsetail poisoning.

  • Weakness, especially in the hind legs
  • Depression
  • Constipation

Lamb’s Quarters (or Pigweed).

This plant is sometimes called goosefoot or pigweed in some regions. The leaves are whitish in color and can have a wide variety of shapes. The stems can be smooth or have a reddish tint. It looks a lot like a small cluster of pale green cauliflowers. It is a common weed in gardens.

Toxin would be effective, a horse must eat large quantities of lamb’s quarters. It is unlikely that a horse would eat this plant unless there is another feed.

3 Symptoms may occur if a horse eats a lot of lamb’s quarters.

  • Weakness
  • Respiratory distress
  • coma
  • Kidney failure

Lily of the Valley

This is a beautiful, spring-blooming perennial flower bulb that can be toxic to horses. Is this something you can grow in your flower garden or yard?

Common garden plants are toxic to pets and humans, including horses. Because of its beautiful flowers and red berries, Lily of the Valley is not likely to be found in pastures. If someone throws garden clippings near a fence line, they could be inadvertently ingested. You should dispose of lawn and garden clippings in an area out of reach of horses.

The toxins in the plant can cause damage to the heart. Ingestion may result in in:4

  • An irregular heart rhythm
  • Low blood pressure
  • seizures
  • colic
  • Weakness
  • Death


The common pasture plant milkweed is milkweed. The central stem is a single, elliptical-shaped branch that branches off the leaves. The plant contains a sticky, white sap. The flowers are arranged in a ball-shaped cluster and can be pink or purplish depending on the time of year. The pods reach 3 inches in height and are split open in the fall to release brown seeds. These brown seeds float through the air on fluffy, downy white fibers. Toxic parts of all parts of the plant can be found. All parts of the plant are toxic, including fresh and green plant material, as well as dried plants, accidentally made into hay. Horses will avoid milkweed, as they do with most toxic plants. 1
  • Weakness
  • seizures
  • Respiratory problems
  • coma
  • Death

The host plant for the important monarch butterfly, milkweed, is milkweed. It is safe to plant this flower in areas away from livestock, even though it shouldn’t be in hay fields.


If eaten in large amounts, pigweed can prove to be extremely toxic. Horses will not eat this plant unless they have no other food. This weed can be found in pastures, vegetable gardens, roadsides, barnyards, and other places. If dried, it can still be toxic when made into hay. Kidney failure can be caused by pigweed or its relative lamb’s quarters. 3 are some other symptoms of pigweed consumption.

  • Muscle tremors and weakness
  • Lack of coordination
  • Kidney failure

Red Maple

The bark of red maples has a smooth, grayish texture. The twigs are reddish brown.

Horses can become ill from fallen and wilted leaves. The toxins can cause damage to the red blood cells. Consuming 1.5 to 3 pounds of red maple leaves can cause death.

After they have fallen, leaves can be toxic for up to several weeks. red maple leaves should not be disposed of in compost piles or manure piles. If red maple leaves are blasted into hay, it can cause serious problems.

Red maples are found throughout the eastern United States as well as Canada.

Red maple poisoning symptoms are: 1

  • breathing difficulties
  • jaundice
  • Dark brown urine
  • Death

Red Oak

There are many varieties of oaks that grow in North America. Horses will eat leaves if they have no other food. Fallen leaves can cause water contamination. Consuming large quantities of acorns can also make them toxic.

1 These are the signs of oak poisoning.

  • poor appetite
  • weight loss
  • diarrhea
  • Increased drinking
  • Increased urination
  • Kidney failure
  • Edema
  • Death

St. John’s Wort

  • St. John’s Wort flowers from May through August. It can tolerate all soil types but prefers moist soil that has good drainage. It will leave a rusty-reddish stain if you crush it between your fingers. St. John’s Wort can cause photosensitivity in livestock. White areas of the skin may become more susceptible to sunburn.

Call your veterinarian immediately if you suspect that your pet may be sick. Your veterinarian is the best person to consult for health questions. They have seen your pet and know your pet’s history.

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