Can they eat it? / Oleander
Can horses eat oleander?
Never. A few leaves can be fatal.
Common as a hedge in the South and West. Dried leaves in hay or clippings are as dangerous as fresh. It acts on the heart.
Colic, drooling, irregular heartbeat, weakness, death.
Call your vet now. Note what was eaten, how much and when; do not wait for signs.
Why it is dangerous
Oleander contains cardiac glycosides, compounds that act on the heart muscle and disrupt its electrical rhythm. The whole plant is toxic, and the leaves are the most dangerous part. Dried leaves stay toxic, so oleander clippings that end up in hay or a pile of trimmings are just as risky as the fresh plant. Even a small amount can cause serious heart trouble, and the effects can be fatal.
How much is too much
There is no safe amount of oleander for a horse. A few leaves can be fatal to a 1,000 lb horse, and a pony or miniature needs far less to be harmed. Because a single bite can do serious damage, treat any exposure as an emergency regardless of how small it looked. Do not wait to see whether signs develop before calling your vet.
Horses
Full-size horses in work or at pasture are at risk wherever oleander grows near fence lines, hedges, or field edges. Horses may nibble hedge clippings or pick leaves from low branches, and dried cuttings can be mixed into hay. Check fencing and keep trimmings well away from paddocks and feed areas. If you suspect any exposure, call your vet right away and note what was eaten, how much, and when.
Ponies and easy keepers
Ponies, miniatures, seniors, and easy keepers are especially vulnerable because they may be curious about plants and their smaller body size means less tolerance for toxins. Horses that are insulin-resistant or prone to laminitis are often kept on carefully measured diets and may be more inclined to graze on anything green. Keep these horses away from oleander entirely, and call your vet immediately at the first sign of any exposure.
Safe alternatives
Offer safe forage such as good-quality grass hay or pasture grass, which horses can graze throughout the day. For a treat, use a small amount of carrot or apple cut into slices, served plain. Provide a salt block so your horse can meet its mineral needs and reduce interest in unfamiliar plants.
Questions people ask
Is oleander dangerous in hay?
Yes. Dried oleander leaves remain toxic, so clippings mixed into hay can poison a horse. Inspect hay carefully and never feed hay that may contain oleander trimmings.
My horse ate oleander after a frost. What should I do?
Call your vet immediately. Frost does not reduce the toxicity of oleander, and waiting for signs can be dangerous. Note what was eaten, how much, and when.
How much oleander is fatal to a horse?
A few leaves can be fatal to a 1,000 lb horse, and smaller horses are at greater risk. There is no safe amount, so any ingestion needs immediate veterinary attention.
Toxic for horses means: do not give it; if they ate it, call your vet or a poison line.
General information from veterinary guidance, not a diagnosis. If you are worried, call your vet or a pet poison line: ASPCA Animal Poison Control (888) 426-4435. Charges may apply.
Written by Hoofdeck editors · updated Nov 13, 2026 · from ASPCA Animal Poison Control, Merck Veterinary Manual and university extension guidance.