What Can Horses NOT Eat? 50+ Toxic Foods and Plants to Avoid [2026]

Knowing what horses cannot eat has gotten complicated with all the well-meaning but sometimes inaccurate advice people share online. As someone who nearly poisoned my horse with a garden plant I didn’t know was toxic, I learned everything there is to know about dangerous foods, plants, and substances. Today, I will share it all with you.

That incident scared me straight. A red maple branch had fallen over the fence line after a storm, and my gelding was happily munching the wilted leaves when I found him. Wilted red maple leaves destroy red blood cells in horses. We got lucky — caught it early, vet came out, he was fine. But I spent the next two weeks identifying every single plant on my property and researching every food anyone had ever suggested giving a horse.

Why Food Safety Matters for Horses

Here’s the thing most people don’t realize about horses: they cannot vomit. Physically impossible. Their digestive system is a one-way street. So if your horse eats something toxic, it’s going through the entire system. There’s no quick fix, no “let’s just get it back up.” That makes prevention absolutely everything.

According to the American Association of Equine Practitioners, a significant number of emergency vet calls involve accidental ingestion of toxic substances. A little knowledge goes a long way toward preventing a crisis.

Fruits and Vegetables to Avoid

Definitely Toxic

Probably should have led with this section, honestly. These are the ones you absolutely need to know:

Food	Danger Level	Why It’s Dangerous
Avocado	HIGH	Contains persin, which causes heart damage and respiratory distress. All parts of the plant are toxic, including the leaves.
Onions/Garlic	HIGH	Damages red blood cells, leading to anemia. This includes cooked onions, garlic powder, and anything in the allium family.
Tomatoes	HIGH	Part of the nightshade family. Contains solanine, which is toxic to horses. The leaves and stems are the worst, but the fruit isn’t safe either.
Potatoes (green/raw)	HIGH	Solanine poisoning causes neurological effects. Green potatoes and potato plants are especially dangerous.
Rhubarb	HIGH	High oxalic acid content causes kidney damage. The leaves are the most concentrated source.
Persimmons	MODERATE-HIGH	The seeds can cause intestinal blockages. Even the fruit in large amounts can form masses in the gut.

Proceed with Extreme Caution

These fall into a gray area, but I err on the side of just not offering them:

Grapes/Raisins: Proven toxic to dogs, and the research on horses is still unclear. I just don’t risk it. There are plenty of safe treats available.
Stone fruit pits: Cherry, peach, plum, apricot — the fruit flesh is generally fine, but the pits contain cyanide compounds. Always remove pits before offering stone fruits.
Apple seeds: Contain amygdalin which converts to cyanide. A few seeds from normal apple treating won’t hurt, but don’t feed a bucket of apple cores.

Plants That Are Toxic to Horses

This is the one that keeps me up at night. Many common plants — including stuff you might have growing in your yard right now — can kill a horse.

Extremely Toxic Plants (Can Be Fatal)

I memorized this list and I suggest you do too:

Plant	Effects	Notes
Yew	Sudden death from heart failure	All parts toxic. Often kills so fast there are no symptoms to observe. A handful of leaves can be fatal.
Red Maple	Destroys red blood cells	Wilted or dried leaves are the most dangerous form. This is the one that nearly got my horse.
Oleander	Heart failure, death	Every part is highly toxic. Even the smoke from burning oleander branches is dangerous.
Rhododendron/Azalea	Cardiac effects, colic, death	Extremely common landscape plant. People don’t realize how dangerous these are around horses.
Water Hemlock	Violent seizures, death within hours	Considered one of the most toxic plants in North America. Grows near water sources.
Poison Hemlock	Respiratory paralysis	Looks disturbingly similar to wild carrot. Learn to tell them apart.

Highly Toxic Plants

Not immediately fatal like the ones above, but still very dangerous:

Foxglove: Cardiac glycosides cause serious heart problems
Lily of the Valley: Same cardiac toxins as foxglove
Ragwort/Tansy: Causes cumulative liver damage. The scary part is that damage builds up silently over time until the liver fails. By the time you see symptoms, it’s often too late.
Sorghum/Sudan Grass: Produces cyanide, especially when stressed by frost or drought
Black Walnut: The shavings cause severe laminitis. Even a small percentage of black walnut mixed into regular shavings can founder a horse within hours.
Locoweed: Neurological damage from chronic consumption
Nightshade family: Belladonna, jimsonweed, and their relatives are all bad news

Moderately Toxic Plants

Less likely to kill but can still cause real problems:

Bracken Fern: Prolonged consumption causes thiamine deficiency
Buttercups: Cause mouth blisters and colic, though most horses avoid them because they taste bitter. Drying eliminates the toxin, so buttercups in hay are generally not an issue.
Milkweed: Contains cardiac glycosides
St. John’s Wort: Causes photosensitivity — horses develop severe sunburn-like reactions
Hoary Alyssum: Causes dramatic leg swelling and can trigger founder
Clover (under certain conditions): Infected clover can cause slobbers (excessive drooling) or photosensitivity. The clover itself isn’t the problem; it’s a fungus that grows on it.

Human Foods That Are Dangerous

Never Feed These

That’s what makes being careful about human food endearing to us horse owners — we know that what seems harmless to us can be genuinely dangerous to them.

Food	Why It’s Dangerous
Chocolate	Theobromine toxicity causes colic, seizures, and can be fatal in large amounts. No, not even a little piece.
Caffeine	Heart arrhythmias and dangerous hyperactivity. This includes coffee grounds, tea, energy drinks.
Alcohol	Liver damage and central nervous system depression. Horses are far more sensitive to alcohol than humans.
Dairy Products	Horses are lactose intolerant as adults. Milk, cheese, yogurt — all cause digestive upset.
Meat/Fish	Horses are herbivores. Their digestive system is not equipped to process animal protein.
Processed Foods	Excessive salt, preservatives, and artificial ingredients are harmful. If it came from a package, keep it away from your horse.

Avoid or Strictly Limit

Bread: Can cause choke and has almost no nutritional value for horses. I know people who toss their stale bread to the horses, and I always discourage it.
Baked goods: Sugar, flour, additives — none of it belongs in a horse
Candy: Sugar overload and artificial ingredients
Chips and salty snacks: Way too much sodium
Lawn clippings: This is the one that catches people off guard. Grass clippings ferment rapidly and can cause severe colic. Plus they might contain toxic plants or lawn chemicals. Never dump clippings into the pasture.

Feed-Related Dangers

Moldy or Spoiled Feed

Mold produces mycotoxins that can cause a terrifying list of problems:

Colic
Liver damage (sometimes irreversible)
Neurological problems
Reproductive issues in broodmares
Death in severe cases

Never feed:

Hay with visible mold (white, blue, or dark patches)
Grain that smells musty or off
Feed that got wet and then dried — mycotoxins don’t go away just because the feed dried out
Anything past its expiration or use-by date

Cattle Feed and Supplements

This section is critical if your property has other livestock:

Ionophores (monensin, lasalocid): Found in cattle feed and FATAL to horses. Even tiny amounts can kill. This is one of the most common causes of horse poisoning on mixed-species farms. It keeps me up at night.
Cattle mineral blocks: Often contain copper levels that are toxic to horses. Always use horse-specific mineral blocks.
Medicated feeds for other species: Many additives perfectly safe for cattle, sheep, or chickens will poison a horse

CRITICAL: Always store horse feed completely separate from other livestock feed. Label everything clearly. One accidental cross-contamination can be fatal.

Toxic Substances Around the Barn

Chemicals and Cleaners

Horses are curious and will investigate (and sometimes taste) things they shouldn’t:

Rodent poisons — keep these completely inaccessible to horses
Insecticides and fly sprays in concentrated form
Herbicides applied to pastures (follow label instructions for grazing restrictions)
Antifreeze — the sweet taste attracts animals, but it’s deadly. Clean up any spills immediately.
Lead paint in older barn buildings
Fertilizers, especially if horses can access storage areas

Bedding Dangers

Black walnut shavings: Causes severe laminitis within hours of contact. Even a 5% contamination of regular shavings can trigger it. Always know your shavings source.
Treated wood shavings: Pressure-treated or chemically preserved wood releases toxins
Cedar shavings: The aromatic oils cause respiratory irritation and may be toxic in quantity

Signs of Poisoning in Horses

Knowing these warning signs can save your horse’s life:

Immediate/Acute Symptoms

Colic signs — pawing, rolling, looking at their sides, refusing to eat
Excessive salivation or drooling
Difficulty breathing or increased respiratory rate
Rapid or irregular heart rate
Trembling, muscle twitching, or staggering
Seizures
Collapse

Gradual/Chronic Symptoms

These are trickier because they develop slowly:

Weight loss despite eating adequate amounts
Dull, poor coat condition that doesn’t improve with grooming
Photosensitivity — sunburn-like reactions on light-skinned areas
Behavioral changes, lethargy, or depression
Reduced appetite
Jaundice — yellowing of the gums and whites of the eyes, indicating liver involvement

What to Do If Your Horse Eats Something Toxic

I have this protocol memorized. You should too:

Stay calm. Panicking doesn’t help your horse. Deep breath.
Remove access to whatever they ate. Get them away from the source immediately.
Call your veterinarian. Right now. Not in five minutes, not after you Google it. Call.
Document everything: What was eaten, approximately how much, and when you noticed. Your vet needs this information.
Don’t try to induce vomiting. Horses physically cannot vomit. Don’t waste time trying.
Save a sample of the plant or substance if you can do so safely. Your vet may need to identify it.
Keep your horse as calm as possible while waiting for the vet.

Emergency contacts to have posted in your barn: Your vet’s regular and after-hours numbers, and the ASPCA Animal Poison Control Center at 888-426-4435. I have both on a laminated card by the barn door.

Prevention Checklist

Pasture Safety:

Walk your pastures regularly to identify toxic plants. I do this seasonally, at minimum.
Remove or fence off dangerous trees — red maple, yew, and black walnut especially
Never throw garden clippings over the fence into horse areas
Test soil and water quality annually
Keep pastures well-maintained so horses have adequate grazing and don’t resort to eating undesirable plants out of hunger

Feed Storage:

Store all feed in sealed, rodent-proof containers
Keep horse feed completely separate from other livestock feed — I can’t stress this enough
Check expiration dates regularly
Inspect for mold before every single feeding
Lock feed rooms. Horses that break into the feed room and gorge can founder or colic severely.

Barn Safety:

Store all chemicals, cleaners, and medications completely out of reach
Use only horse-safe bedding from verified sources
Check for lead paint if you’re in an older barn
Secure trash cans so horses can’t investigate the contents

Quick Reference: 50+ Foods/Substances to Avoid

Fruits/Vegetables: Avocado, tomatoes, raw/green potatoes, onions, garlic, rhubarb, persimmons

Plants: Yew, red maple, oleander, rhododendron, water hemlock, poison hemlock, foxglove, lily of the valley, ragwort, nightshade, locoweed, bracken fern, milkweed, sorghum, hoary alyssum

Human Foods: Chocolate, caffeine, alcohol, dairy products, meat, large amounts of bread, candy, processed foods

Feed: Moldy hay or grain, cattle feed containing ionophores, medicated feeds formulated for other species

Substances: Rodent poison, antifreeze, fertilizers, herbicides, black walnut shavings, treated wood

The Bottom Line

When it comes to toxic substances and horses, prevention is everything. Take the time to educate yourself, inspect your property thoroughly, and build safe habits around feeding and pasture management. Print this list and put it in your barn if it helps.

When you’re not sure whether something is safe, the answer is simple: don’t risk it. Stick to proven-safe treats like carrots, apples (minus the seeds), bananas, and watermelon. And when in doubt, call your vet. Better to make a “silly” phone call than to deal with the alternative.

Sources: American Association of Equine Practitioners, ASPCA Animal Poison Control, University of California Davis Veterinary Medicine, Kentucky Equine Research