Are Walnut Trees Toxic to Pets? Black Walnut Risks

Name: Are Walnut Trees Toxic to Pets? Black Walnut Risks
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-03

Are all walnut trees toxic to pets? No. The tree that causes the most concern in the United States is the black walnut (Juglans nigra), and even then, the danger depends on the part of the tree and whether mold is present. The ASPCA Animal Poison Control Center lists black walnut as toxic to dogs and horses but non-toxic to cats [1]. This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Black walnut is listed as toxic to dogs and horses, and non-toxic to cats, by the ASPCA Animal Poison Control Center [1].
The biggest danger to dogs is moldy black walnut nuts and hulls, which can cause tremors and seizures [1].
Black walnut wood shavings can cause incoordination in dogs that ingest them [1].
If your pet ate any part of a walnut tree, call your veterinarian, the ASPCA Animal Poison Control Center at (888) 426-4435, or Pet Poison Helpline at (855) 764-7661 right away.
Do not make your pet vomit unless a veterinarian tells you to.

Are All Walnut Trees Toxic to Dogs and Cats?

The short answer is no, but the details matter. The ASPCA lists black walnut (Juglans nigra) as toxic to dogs and horses, with cats listed as non-toxic [1]. That does not mean cats should be allowed to chew on walnut wood or eat moldy nuts. It means the specific toxic principle tracked by the ASPCA has not been shown to cause the same problems in cats.

Other walnut species, such as English walnut (Juglans regia), are grown for food and are not listed as toxic to pets in the same way. Walnut pollen from Juglans regia has been studied for its antioxidant compounds, and researchers identified 24 phenolic compounds in it, but that work was about chemistry and potential health benefits, not pet poisoning [2]. It does not tell us anything about whether walnut pollen is safe for your dog or cat to eat.

The practical takeaway: black walnut is the species to worry about most, especially the moldy nuts and hulls. If you are not sure what kind of walnut tree is in your yard, treat it as a potential risk and keep your pet away from fallen nuts and wood debris.

Which Parts of the Walnut Tree Are Dangerous?

Moldy Nuts and Hulls

This is the classic black walnut emergency in dogs. When black walnuts fall and sit on the ground, the hulls and nuts can grow mold. Dogs that eat these moldy nuts or hulls can develop tremors and seizures [1]. This is the scenario that sends dogs to the emergency clinic.

The mold itself produces tremorgenic mycotoxins, which are toxins that cause tremors. A case report described a dog that developed whole-body seizures after vomiting parts of compost, and testing found Penicillium mold plus the tremorgenic mycotoxins paxilline, penitrem A, and roquefortine C in the vomit and the compost [3]. That case involved compost instead of walnuts, but it shows how moldy plant material can cause serious neurologic signs in dogs. Moldy black walnuts can carry the same type of risk.

If your dog eats walnuts, including moldy ones, see Can Dogs Eat Walnuts? Black Walnut Mold Toxicity for a focused guide.

Wood, Shavings, and Mulch

Black walnut wood shavings can cause incoordination in dogs that ingest them [1]. This matters if you use walnut shavings as bedding, mulch, or a craft material around the house. Dogs that chew on wood or dig in mulch may swallow pieces.

Fallen Leaves, Twigs, and Bark

The ASPCA record focuses on moldy nuts and hulls and on shavings [1]. Leaves, twigs, and bark are not the main reported problem for dogs and cats, but a pet that eats a lot of any plant material can still get an upset stomach. If your pet eats leaves or bark and then vomits or acts dull, call your veterinarian.

Juglone in Soil and Around the Tree

Black walnut trees produce juglone, a compound that is well known for harming certain plants growing near the tree. Gardeners talk about it often. In veterinary terms, juglone is not the toxic principle the ASPCA lists for black walnut, and its role in pet poisoning is not well established in veterinary research [1]. Do not assume that because juglone kills tomato plants it will poison your dog in the same way. The documented pet risks are the moldy nuts and hulls and the wood shavings [1].

What Is the Toxic Principle and What Does It Do?

For black walnut, the ASPCA lists the toxic principle as unknown [1]. That is an honest answer. Veterinary toxicologists have not pinned down a single compound that explains every sign.

What we do know is that two separate problems show up in dogs:

Moldy nuts and hulls. These can carry tremorgenic mycotoxins from mold. These toxins affect the nervous system and can produce tremors and seizures [1][3]. The mold grows on the nut material, so the danger increases when nuts sit on damp ground.
Wood shavings. Ingesting black walnut shavings can cause incoordination, which means your dog may stumble, sway, or have trouble walking [1].

In horses, black walnut exposure has been linked to laminitis and colic [1]. That is a separate species concern, but it is worth knowing if you keep horses near walnut trees.

What Are the Signs and How Fast Do They Appear?

Signs depend on what your pet ate.

Dogs that ate moldy black walnuts or hulls:

Tremors or shaking
Seizures
Vomiting
Acting disoriented or unsteady

These are the signs the ASPCA lists for dogs eating moldy nuts and hulls [1]. In the published case of tremorgenic mycotoxin poisoning, the dog had an acute onset of whole-body seizures and had vomited compost shortly before [3]. Acute means the signs came on suddenly, within a short time of eating.

Dogs that ate black walnut shavings:

Incoordination
Trouble walking or standing steadily

This is the sign the ASPCA lists for shavings ingestion [1].

Cats: The ASPCA lists black walnut as non-toxic to cats [1]. That does not guarantee a cat will feel fine after eating a moldy nut. Cats are smaller and can react to moldy food with vomiting or diarrhea. If your cat eats any walnut material and seems off, call your veterinarian.

Timeline: Tremorgenic mycotoxin signs tend to come on quickly after ingestion, often within hours. In the reported case, the dog recovered fully within 24 hours of intensive care [3]. That is encouraging, but it also shows how serious the signs can be before treatment starts. Do not wait to see if tremors pass on their own.

What to Do Right Now

If you saw your pet eat any part of a walnut tree, act now.

Remove your pet from the area. Pick up any remaining nuts, hulls, or wood pieces so your pet cannot eat more.
Call for help. Contact your veterinarian, the ASPCA Animal Poison Control Center at (888) 426-4435, or Pet Poison Helpline at (855) 764-7661. Have the following ready: your pet's weight, what you think was eaten, how much, and when.
Do not induce vomiting unless a veterinarian tells you to. Making a pet vomit can cause harm, especially if the pet is already showing neurologic signs like tremors or seizures.
Do not give food, milk, oil, or home remedies. These do not treat poisoning and can complicate treatment.
Save a sample if you can. If your pet vomited, collect it in a sealed bag or container. If there are leftover nuts or hulls, keep a few for identification. This helps your veterinarian and the poison control team.
Go to the clinic if signs are present. Tremors, seizures, stumbling, or repeated vomiting mean your pet needs to be seen now, not in the morning.

If your pet ate a plant and you are not sure whether it was toxic, Dog Ate Toxic Plant walks through the first steps. For a broader list of dangerous plants, see Plants Poisonous To Dogs.

How Veterinarians Treat Black Walnut Exposure

Treatment depends on what your pet ate and how sick they are. Your veterinarian will start with a physical exam and questions about the exposure.

Decontamination. If your pet just ate the material and is stable, your veterinarian may induce vomiting in the clinic. They may also give activated charcoal to bind toxins still in the gut. Whether this is safe depends on your pet's neurologic status and how long ago the ingestion happened.

Seizure and tremor control. If your dog is having tremors or seizures, the priority is stopping them. Your veterinarian will choose a medication and dose based on your dog's weight and condition. The dose is calculated for your pet, so there is no single number that applies to every dog.

Supportive care. This can include intravenous fluids, anti-nausea medication, and monitoring. In the published case, the dog received immediate decontamination plus supportive treatment and recovered fully within 24 hours of intensive care [3].

Monitoring. Dogs with neurologic signs need close watching until the signs stop and stay stopped. Some pets need to stay overnight.

If your pet has a known allergy history, mention it. Walnut allergy is well documented in people, and researchers have identified several walnut proteins that trigger reactions, including storage proteins and lipid transfer proteins [4]. Food allergy is different from poisoning, but your veterinarian should know your pet's history.

What Is the Outlook?

The outlook is good for many pets that get prompt treatment. The dog in the published tremorgenic mycotoxin case recovered fully within 24 hours of intensive care [3]. That is one case, and every pet is different, but it shows that fast veterinary care can lead to a full recovery.

The outlook is worse when treatment is delayed, when seizures are prolonged, or when a pet has other health problems. Pets that eat a large amount of moldy material or that keep having seizures despite treatment need more intensive care.

For black walnut shavings ingestion, incoordination often improves once the material clears and the pet is supported [1]. Your veterinarian will tell you what to expect based on your pet's exam.

Prevention and Safer Alternatives

Prevention is simpler than treatment.

Rake up fallen walnuts. Do this daily during drop season. Moldy nuts are the main hazard for dogs [1].
Fence off the tree area. A simple garden fence keeps dogs away from nuts, hulls, and wood debris.
Skip black walnut mulch and shavings. Choose pet-safe mulch instead. Cedar and pine are common choices, but check with your veterinarian if your pet likes to chew on bedding or mulch.
Supervise outdoor time. Dogs that scavenge need eyes on them, especially in yards with nut trees.
Store craft wood away from pets. Black walnut is popular for woodworking. Keep scraps and shavings out of reach.
Pick pet-safe plants. If you are choosing new trees or shrubs, look at Plants That Aren't Toxic To Cats And Dogs for options.
Watch for other tree hazards. Fallen pits and seeds from other trees can also be a problem. My Dog Ate a Peach Pit: Is It a Choking Hazard or Toxic? covers one common example.

Limitations and When to Contact a Veterinarian

No article can tell you what is happening inside your specific pet. Individual cases need a veterinarian who can examine your pet, ask about the exposure, and run tests if needed.

Call now (emergency):

Seizures of any kind
Tremors or whole-body shaking
Stumbling, swaying, or trouble standing
Repeated vomiting
Collapse, weakness, or unresponsiveness

Call the same day:

You saw your pet eat moldy walnuts, hulls, or black walnut shavings, even if your pet seems fine right now
Your pet vomited once after eating walnut material
Your pet ate an unknown amount of walnut material
Your cat ate any walnut material and is not acting normal

Routine visit:

Your pet has mild stomach upset after nibbling plant material and is otherwise bright and alert
You want advice on pet-safe landscaping around a walnut tree

When in doubt, call. Poison control lines are staffed to help you decide whether your pet needs to be seen. The ASPCA Poison Control number is (888) 426-4435 and Pet Poison Helpline is (855) 764-7661.

Frequently Asked Questions

Are all walnut trees toxic to pets?

No. Black walnut is the species listed as toxic to dogs and horses, while cats are listed as non-toxic [1]. Other walnut species grown for food are not tracked as a pet poisoning risk in the same way. The parts that matter most are moldy nuts and hulls and wood shavings [1].

Can my dog get sick from eating a walnut off the ground?

Yes, if the walnut is moldy. Moldy black walnut nuts and hulls can cause tremors and seizures in dogs [1]. Nuts that have sat on damp ground are the highest risk. Call your veterinarian or a poison control line if your dog eats one.

What does black walnut poisoning look like in a dog?

The main signs are tremors and seizures after eating moldy nuts or hulls, and incoordination after eating shavings [1]. Vomiting can happen too. Signs often come on suddenly, so do not wait to see if they pass.

Are walnut trees safe for cats?

The ASPCA lists black walnut as non-toxic to cats [1]. That said, cats can still get an upset stomach from eating moldy plant material. If your cat eats walnut material and vomits or acts dull, call your veterinarian.

Should I make my dog vomit after eating a walnut?

No, not unless a veterinarian tells you to. Inducing vomiting at home can be dangerous, especially if your dog is already showing neurologic signs. Call your veterinarian, the ASPCA Animal Poison Control Center at (888) 426-4435, or Pet Poison Helpline at (855) 764-7661 and follow their instructions.

References

Toxic and Non-toxic Plants: Black Walnut. ASPCA Animal Poison Control Center.
Phytochemical Screening and Bioactive Properties of Juglans regia L. Pollen. Antioxidants (Basel, Switzerland), 2022.
Tremorgenic mycotoxin poisoning in a dog: A case report. Veterinarni medicina, 2023.
Walnut Allergy Across Europe: Distribution of Allergen Sensitization Patterns and Prediction of Severity. The journal of allergy and clinical immunology. In practice, 2021.