Why it's dangerous
The plant contains toxalbumins which inhibit protein synthesis and cause gastrointestinal and neurological distress.
Toxic compound: Toxalbumins (robin, phasin, and robitin)
How vets treat it
No treatment plan written for dogs was found, and there is no specific treatment. Colorado State University describes supportive care, including activated charcoal, and IV fluids for dehydration and shock in severe cases. The Merck Veterinary Manual also recommends supportive care. Both sources write mainly about livestock and horses.
Outlook
No source gives an outlook for dogs. Pet Poison Helpline describes moderate to severe stomach and gut signs in pets, and the ASPCA lists death among the possible signs. In grazing animals, mostly horses, the Merck Veterinary Manual says death is infrequent but recovery can take a long time.
Where pets are exposed
- Black locust trees (Robinia pseudoacacia), also called false acacia or locust tree. Native to the eastern and central United States, they are often planted as ornamentals and grow wild in open woods, along roadsides and along waterways.
- In Europe, black locust is among the plants that commonly poison livestock and horses.
- The bark, seeds and leaves, which contain the toxins. The bark and seeds have the highest levels, and new growth is the most toxic.
- Seed pods: flat, brown pods with several seeds each, which hang on the tree and may stay there through winter.
- Young trees and new shoots, which carry sharp thorns. The tree also sends up suckers from its roots, so young shoots can come up away from the trunk.
- Fragrant white flowers that hang in clusters in spring and early summer. Sources disagree about whether the flowers are toxic.
Prevention
- Don't let pets chew black locust bark, branches or sticks, or play with the seed pods. The bark and seeds carry the most toxin.
- Pick up fallen pods, seeds and pruned branches where your pet plays.
- Remove young black locust shoots and suckers from your yard: new growth is the most toxic, and the tree sends up shoots from its roots.
- If you're not sure which trees grow in your yard, have an expert or a local plant nursery identify them.
Good to know
All parts of the plant are toxic, with the seeds and bark containing the highest concentration of toxins.
Common questions
Is black locust toxic to dogs?
Yes. The ASPCA lists black locust as toxic to dogs, cats and horses. The bark, leaves and seeds contain toxic proteins called toxalbumins, such as robin and phasin, which stop cells from making proteins and can kill them. Pet Poison Helpline says eating the plant causes moderate to severe stomach and gut signs in pets, and the ASPCA lists vomiting, weakness, bloody diarrhea and death among the signs. Call your vet or a pet poison line right away if your dog chews any part of the tree.
Is black locust toxic to cats?
Yes. The ASPCA lists black locust as toxic to cats, and Pet Poison Helpline says eating the plant causes moderate to severe stomach and gut signs in pets. None of the sources we checked describes a case in a cat or gives a toxic amount, so treat any chewing as urgent and call your vet.
Which parts of a black locust tree are poisonous?
The bark, seeds and leaves contain the toxins, and Pet Poison Helpline says all parts of the plant do. Colorado State University says the bark and seeds have the highest levels and new growth is the most toxic. Besides the toxic proteins, Merck and NC State Extension name a glycoside, robitin. The amount of toxin varies from tree to tree with growing conditions.
Are black locust flowers toxic to pets?
Sources disagree. Poison Control says the flowers appear to be nontoxic or much less toxic than the rest of the tree, and NC State Extension lists them as edible. But Pet Poison Helpline says all parts of the plant contain the toxins, and the Merck Veterinary Manual says they are found throughout the plant. No source says the flowers are safe for dogs or cats, so call your vet if your pet eats them.
Why do most black locust reports involve horses?
Most published poisonings involve grazing animals. The Merck Veterinary Manual says black locust affects all grazing animals, mostly horses, Colorado State University lists horses, cattle, chickens and children as the ones affected, and in Europe it is among the plants that commonly poison livestock and horses. Don't use figures from those reports to judge your pet's risk. Dogs and cats are still at risk: the ASPCA lists the tree as toxic to both, and Pet Poison Helpline describes moderate to severe stomach and gut signs in pets.
My dog chewed a black locust stick or seed pod. What should I do?
Call your vet or a pet poison line now, even if your dog seems fine: the bark and seeds carry the most toxin. Take away what's left, don't make your dog vomit unless a vet tells you to, and note roughly how much your dog chewed and when. Go to an emergency vet if your dog vomits repeatedly, has bloody diarrhea, seems weak or has trouble breathing.
Sources
- Merck Veterinary Manual — Range Plants of Temperate North America
- ASPCA Animal Poison Control Center — Toxic and Non-toxic Plants: Locust
- Pet Poison Helpline — Black Locust
- Pet Poison Helpline — Emergency Instructions
- Colorado State University, College of Veterinary Medicine and Biomedical Sciences — Guide to Poisonous Plants: Black Locust
- NC State Extension Gardener Plant Toolbox — Robinia pseudoacacia (Black Locust)
- National Capital Poison Center (Poison Control) — Are Black Locust Trees Toxic?
- The Veterinary Journal (via PubMed, PMID 23570777) — Cortinovis C, Caloni F. Epidemiology of intoxication of domestic animals by plants in Europe (2013, abstract)
- Pet Poison Helpline
This page is informational and is not veterinary advice. If your pet has been exposed to something risky, contact your vet or an animal poison control line right away.
