Wildflowers that are Toxic to Horses

Horses are smart animals and will usually avoid eating plants that are poisonous to them. However, it is important to know which wildflowers are toxic to horses so as to avoid mowing them for hay or planting them in your field. You may also remove them if they are present. Here are a few common wildflowers that are toxic to horses.

Common Milkweed (Asclepias syriaca)

Milkweed (Asclepias spp.)

The Common Milkweed is a North American native perennial characterized by clusters of fragrant, pink, or purple flowers that bloom in the summer. They are a good nectar source for hummingbirds, bees, and butterflies.

However, it is extremely toxic to horses. Milkweed produces a milky substance containing cardenolides and galitoxin, poisonous to horses.

Horses will typically avoid it, but removing it from your farm is best. It thrives in USDA hardiness zones 3-9. Milkweed requires full sunlight and does well in medium moisture, well-drained soils. 

Buttercup (Ranunculus spp.)

Buttercup. Photo by Timo Newton-Syms

Buttercup is popular for its bright yellow flowers. They grow well in moist, well-drained clay soils near woodland areas. The entire plant is toxic to horses. Buttercups produce ranunculin, a compound that irritates when it is disturbed by chewing.

Horses who feed on the plant have blisters in their mouths and might suffer from digestive issues. Most horses will avoid buttercups due to their poor taste. Thrives in USDA hardiness zones 7-8. 

Mountain Laurel (Kalmia latifolia)

Mountain Laurel (Kalmia latifolia)
Photo by Thomas Quine

Mountain Laurel1 is an evergreen shrub native to North America. All parts of the plant are toxic if ingested. It leads to stomach irritation and possibly abdominal pain in horses. It is characterized by bright pale pink flowers blooming in late spring and early summer.

Its foliage turns from light green to dark green across the year. It thrives in USDA zones 4-9, under full or partial sunlight and moist, well-drained, acidic soils. 

White and red clover

Clover (Trifolium spp.)
white clover

White and red clover are toxic to horses. They produce slaframine, which causes horses to be affected by slobbers. The chemical stimulates the salivary glands and causes the horses to drool.

If a horse is affected by clover, give it plenty of fresh water. Clovers thrive in USDA zones 3-10, under full or partial sunlight, and in well-drained acidic soils.


  1. https://www.fs.fed.us/database/feis/plants/shrub/kallat/all.html