If you have dogs, cats, or horses and buckthorn grows on your property, this is something worth knowing: buckthorn is toxic to pets and livestock. Both common buckthorn (Rhamnus cathartica) and glossy buckthorn (Frangula alnus) — the two species widely established in Lake County and Northern Cook County — contain toxic compounds in their berries, bark, and leaves.
This post covers what makes buckthorn toxic, what symptoms to watch for, and what to do if your pet eats any part of the plant.
If your pet has already ingested buckthorn, call the ASPCA Animal Poison Control Center at (888) 426-4435 or the Pet Poison Helpline at (855) 764-7661, and contact your veterinarian immediately.
What Makes Buckthorn Toxic?
Buckthorn contains anthraquinone glycosides — including emodin in common buckthorn, and frangulin A and B in glossy buckthorn — that are powerful purgatives (compounds that cause rapid, severe emptying of the digestive tract). These are the same class of compounds historically used in human laxative products like cascara, which was derived from the bark of Frangula alnus.
In pets, these compounds cause dose-dependent gastrointestinal distress. Even a relatively small amount of berries can cause symptoms in a small dog or cat.
Which Parts Are Toxic?
All parts of the plant should be considered potentially harmful:
- Berries: The most commonly ingested part. Small, round, and dark black at maturity. Birds readily eat them (they appear resistant to the purgative effects), but dogs and cats are not.
- Bark: Contains concentrated anthraquinones. Chewing on stems or branches poses a real risk.
- Leaves: Contain toxic compounds in lower concentrations than berries or bark, but should still be avoided.
There is no safe part of the plant for pets to ingest.
Symptoms to Watch For in Dogs and Cats
Symptoms of buckthorn toxicity typically appear within a few hours of ingestion and may include:
- Profuse, watery diarrhea — often the first and most prominent sign
- Vomiting
- Abdominal pain or cramping (your dog may seem hunched, restless, or reluctant to move)
- Excessive drooling
- Lethargy or weakness
- Dehydration from significant fluid loss
In severe cases, or if a large quantity was ingested, electrolyte imbalances can develop — which in extreme situations can affect heart function. This is more likely if symptoms go untreated and dehydration progresses.
What About Horses?
Yes — buckthorn is toxic to horses as well. Horses that graze near buckthorn or consume clippings can develop severe diarrhea and colic. Given a horse's sensitivity to gastrointestinal disruption, buckthorn ingestion can become a serious, fast-developing situation. If you have horses, removing buckthorn from pasture areas and fence lines is a priority.
Are Birds and Deer Affected?
Birds that eat the berries appear largely resistant to the purgative effects — this is actually part of what makes buckthorn so ecologically damaging. Birds can consume buckthorn berries without significant harm and deposit seeds across wide distances, accelerating the plant's spread.
Deer generally avoid buckthorn, which is one reason it spreads so aggressively in deer-populated woodlots: most native vegetation gets browsed while buckthorn is left alone.
What to Do If Your Pet Ingests Buckthorn
Act promptly. Don't wait to see if symptoms develop.
- Call the ASPCA Animal Poison Control Center at (888) 426-4435. There may be a fee, but they have veterinary toxicologists available 24/7.
- Call the Pet Poison Helpline at (855) 764-7661. Another 24/7 resource.
- Contact your own veterinarian. Even if it's after hours, call the emergency line.
- Do not induce vomiting unless specifically instructed by a vet or poison control specialist.
- Bring a sample of the plant (or a photo) to your vet appointment. Knowing which species was ingested helps the vet assess the situation.
Treatment is typically supportive — fluids to address dehydration, and monitoring of electrolytes. Most pets recover fully with prompt care, but time matters.
The Practical Case for Removal
If your dogs, cats, or horses have regular access to your yard or wooded areas, and buckthorn grows in those spaces, removal is the most reliable way to eliminate the risk. Beyond the toxicity concern, buckthorn infestations grow more extensive every year — the longer it stays, the more of your property it occupies and the more costly removal becomes.
We offer free property assessments throughout Lake County and Northern Cook County. Contact us to schedule a walkthrough. We can assess the extent of your infestation, give you an honest picture of the removal scope, and help you decide between professional removal or a DIY approach for smaller areas.
If you live in Riverwoods, Long Grove, or Glenview, there are also municipal cost-share programs that can cover 50% of professional removal costs.