Is Hydrangea Poisonous? – Toxicity to Dogs, Cats, and Humans

Hydrangea is toxic to dogs, cats, and horses. The ASPCA lists it as toxic to all three species. The active toxin is a cyanogenic glycoside found in the leaves, flowers, and buds. In practice, most pet and human exposures result in gastrointestinal symptoms rather than serious cyanide poisoning, but the plant should not be treated as harmless. Contact your vet if your pet has eaten any part of a hydrangea.

How Hydrangea Causes Toxicity

Hydrangea (Hydrangea arborescens and related species) contains cyanogenic glycosides, compounds that can release hydrogen cyanide when metabolized. The ASPCA notes that full cyanide intoxication is rare from hydrangea ingestion and that most exposures produce gastrointestinal disturbance rather than systemic cyanide effects. This is because the concentration of cyanogenic glycosides in hydrangea is lower than in plants like cherry laurel or bitter almonds, and a large quantity would need to be consumed to approach cyanide toxicity thresholds.

Even without reaching cyanide toxicity, the glycosides cause enough irritation to produce significant GI symptoms. In people, hydrangea has a documented history of causing illness when used improperly as a herbal remedy.

Which Parts of Hydrangea Are Toxic?

All above-ground parts of the plant contain cyanogenic glycosides: leaves, flower buds, flowers, and stems. The flower buds and young leaves tend to have higher concentrations than mature flowers. Dried plant material can still be toxic.

Roots also contain these compounds but are not typically the point of exposure for pets or children.

Symptoms of Hydrangea Ingestion

Dogs and cats: Vomiting and diarrhea are the most common signs. Lethargy and loss of appetite can follow. In cases of large ingestion, more serious signs consistent with cyanide-like toxicity could theoretically occur, including weakness, rapid breathing, and collapse, but this outcome is uncommon from typical garden exposure. The ASPCA specifically notes that cyanide intoxication is rare with hydrangea.

Humans and children: Nausea, vomiting, abdominal pain, and diarrhea are typical. There are historical reports of people becoming ill after consuming hydrangea as an herbal tea, with symptoms including dizziness and nausea. Skin contact with cut stems can occasionally cause mild irritation.

What to Do If Someone Ingests Hydrangea

1. Remove any plant material from the mouth.
2. Rinse the mouth with water.
3. Do not induce vomiting unless instructed by a medical professional.
4. Call poison control at 1-800-222-1222 (US) or your vet as soon as possible.
5. Note the approximate amount consumed and which part of the plant was eaten.
6. Watch for worsening symptoms such as weakness, difficulty breathing, or pale gums, and report these immediately.

Most garden-level exposures produce vomiting and diarrhea that resolve with supportive care. Vet contact is still recommended because the cyanogenic nature of the plant means symptoms can theoretically escalate.

Keeping Hydrangeas Safely Around Pets

• Place container hydrangeas out of reach of dogs and cats. Ground-planted hydrangeas in garden beds can be fenced off or grown in areas where pets are not left unsupervised.
• Clean up fallen leaves and spent flowers promptly, as fallen material on the ground is accessible to dogs.
• If your dog is a persistent plant chewer, consider placing the hydrangea in a location the dog cannot access at all.
• Wear gloves when pruning or handling cut stems, particularly if you have sensitive skin.

Hydrangeas are one of the most popular garden shrubs. The risk is real but manageable. Most dogs that chew a leaf or two will experience vomiting and recover without lasting harm. The concern rises proportionally with the amount consumed.

Frequently Asked Questions

Are hydrangeas toxic to dogs? Yes. The ASPCA lists hydrangeas as toxic to dogs. Ingestion causes vomiting, diarrhea, and lethargy in most cases. Contact your vet if your dog has eaten any part of the plant.

Are hydrangeas poisonous to cats? Yes. Cats are also listed as susceptible by the ASPCA. Since cats are smaller, even moderate ingestion relative to body weight warrants prompt veterinary attention.

How much hydrangea would it take to seriously poison a dog? The ASPCA notes that full cyanide toxicity is rare from hydrangea, implying that typical garden chewing does not usually reach dangerous thresholds. However, exact dose data is not well-established, and this is not a reason to delay calling a vet.

Can humans eat hydrangea? No. People have been made ill by consuming hydrangea flowers or leaves, including when brewed as tea. The plant is ornamental, not edible.

Are dried hydrangeas still toxic? Yes. Dried plant material retains the cyanogenic glycosides. Dried flower arrangements or wreaths that include hydrangea should be kept away from pets and out of reach of children who might mouth them.