Is Hydrangea Toxic to Cats and Dogs?
Hydrangea is moderately toxic to both cats and dogs — leaves and flowers contain cyanogenic glycosides, usually causing vomiting and diarrhea. Serious cases are uncommon.
Can cause real harm — call a vet for guidance.
Can cause real harm — call a vet for guidance.
In an emergency, do not wait.
Medical disclaimer: This tool is for general information only and isnot a substitute for veterinary diagnosis or treatment. Toxicity depends on the amount, your pet’s size, and health history. If your pet may have ingested something harmful, contact your veterinarian or a poison control hotline ((888) 426-4435 / (855) 764-7661) immediately — do not wait for symptoms to appear.
What is Hydrangea?
Hydrangea is moderately toxic to both cats and dogs — leaves and flowers contain cyanogenic glycosides, usually causing vomiting and diarrhea. Serious cases are uncommon.
Also known as: hydrangea macrophylla, hortensia, bigleaf hydrangea, hydrangea leaves, hydrangea flowers.
Symptoms to Watch For
🐕 In Dogs
- Vomiting, drooling, and diarrhea within a few hours
- Lethargy and loss of appetite
- Abdominal discomfort
- Rapid recovery is common, but large amounts can cause more serious effects
🐈 In Cats
- Vomiting, drooling, and diarrhea
- Lethargy and reduced appetite
- Abdominal discomfort
- Signs usually appear within a few hours and are usually mild
What to Do If Ingested
- Remove any remaining plant material from the mouth.
- Rinse the mouth with water if there is drooling.
- Offer water and watch closely for a few hours.
- Call a vet if vomiting is repeated or your pet seems unusually lethargic.
Steps apply to both cats and dogs. When in doubt, call a vet or poison hotline before acting. Have a cat? Run the Pet Poison Triage Wizard for cat-specific steps.
When to Call the Vet Immediately
Call your veterinarian or a poison control hotline right away if you notice any of these:
- A large amount of leaves or flowers was eaten
- Persistent vomiting, diarrhea, or lethargy
- Any unusual behavior or breathing changes
Frequently Asked Questions
Frequently Asked Questions
Does hydrangea contain cyanide?
The leaves and buds contain cyanogenic glycosides, which can release small amounts of cyanide when chewed — but in typical household nibbling cases the dose is far too small for cyanide poisoning. The realistic outcome is vomiting, diarrhea, and lethargy. Large ingestions still warrant a vet call.
Which parts of the plant are the problem?
The leaves and flower buds have the highest concentration of the toxin; flowers are lower. Cut hydrangea stems in bouquets also pose a risk, and the flower water can become contaminated. Keep both garden plants and arrangements out of reach.
Will my pet need treatment after eating hydrangea?
Most cases need only monitoring and supportive care — the stomach upset usually resolves within a day. A vet may give anti-nausea medication and fluids. If a large amount was eaten, the vet may induce vomiting or give activated charcoal. Call for guidance rather than waiting if symptoms persist beyond a few hours.
Sources
This entry is reviewed against the following authoritative veterinary sources.
- ASPCA Toxic and Non-Toxic Plants Database
- Merck Veterinary Manual — Toxicology
- Pet Poison Helpline — Poisons
Last reviewed: 2026-10-16