Are hydrangeas toxic? Separating fact from garden myth

September 30, 2025 •

4 min read

According to the ASPCA, hydrangeas are toxic to dogs, cats, and horses because they contain a compound called cyanogenic glycoside. As all parts of the plant, including the beautiful flowers, leaves, and buds, contain these potentially harmful chemicals, it's crucial to understand the answer to the question, 'Are hydrangeas toxic?', especially if you have curious pets or young children.

Quick Summary

Hydrangeas contain cyanogenic glycosides that can cause illness if ingested by humans or pets. Symptoms typically include mild to moderate gastrointestinal upset. Severe cyanide intoxication is rare but possible, particularly with large quantities. Both fresh and dried plants pose a risk.

Key Points

Toxic Compounds: All parts of the hydrangea plant contain cyanogenic glycosides, which can release cyanide when ingested.
Risk to Pets: Hydrangeas are officially classified as toxic to dogs, cats, and horses by the ASPCA.
Risk to Children: Young children are at risk of accidental poisoning due to their tendency to put things in their mouths.
Common Symptoms: Mild to moderate ingestion typically causes gastrointestinal upset, including vomiting and diarrhea, in both humans and pets.
Severe Cases: Although rare, severe poisoning can lead to more serious complications, including respiratory issues and seizures, especially with large amounts ingested.
Skin Irritation: Handling the plant, especially the sap, can cause contact dermatitis in sensitive individuals.
Dried Still Toxic: Dried hydrangea flowers and plants contain concentrated toxins and are also poisonous to animals.
Immediate Action: If ingestion is suspected, contact poison control or a veterinarian immediately; do not wait for severe symptoms.

Understanding Hydrangea Toxicity

Hydrangeas (species including Hydrangea arborescens and Hydrangea macrophylla) are beloved for their vibrant, voluminous flowers, but beneath their beauty lies a toxic compound known as cyanogenic glycoside. When the plant's tissues are chewed or crushed, this substance can release cyanide, a potent toxin. While the danger is real, the severity of poisoning largely depends on the amount ingested and the size of the individual. Most cases involving pets and humans result in mild gastrointestinal issues, with life-threatening cyanide poisoning being extremely rare due to the amount that would need to be consumed.

Toxicity for Humans

In humans, accidental ingestion of hydrangea is uncommon, but it can pose a risk, particularly for young children who may put things in their mouths. Ingesting parts of the plant can cause uncomfortable symptoms such as nausea, vomiting, and diarrhea. In rare, more severe cases involving large consumption, central nervous system complications like lethargy, breathing issues, or seizures could occur. Beyond ingestion, some individuals, especially those with high skin sensitivity or florists who handle the plant frequently, can experience allergic contact dermatitis from touching the plant's sap.

Toxicity for Pets

For pet owners, the risk is more significant because dogs and cats are more likely to chew on garden plants. The ASPCA confirms that hydrangeas are toxic to dogs, cats, and horses. Common symptoms of ingestion in pets include vomiting, lethargy, depression, and diarrhea. Small dogs and cats are more vulnerable as they need to consume less of the plant material to cause an issue. It is also important to remember that dried hydrangeas are just as, if not more, toxic, as the cyanogenic glycosides can become concentrated.

Symptoms of Hydrangea Poisoning

If you suspect that a person or pet has ingested part of a hydrangea plant, knowing the potential symptoms is critical for a quick response. While the severity can vary widely, these are the signs to watch for:

Symptoms in Humans and Children

Gastrointestinal Distress: Stomach pain, nausea, vomiting, and diarrhea are the most common signs.
Allergic Reaction: Skin irritation, redness, and rash (contact dermatitis) can occur from handling the plant's sap.
Severe Symptoms: In cases of significant ingestion, look for shortness of breath, dizziness, a rapid pulse, or convulsions.

Symptoms in Pets (Dogs and Cats)

Digestive Upset: The most frequent symptoms include vomiting and diarrhea.
Lethargy and Depression: Your pet may appear unusually tired, weak, or withdrawn.
Other Signs: Look for a decreased appetite, excessive drooling, or a racing heart rate.
Severe Signs: In very rare, extreme cases, difficulty breathing, seizures, or coma can occur.

Comparison of Hydrangea Toxicity Risks


Group	Common Symptoms of Ingestion	Risk Level	Important Considerations
Humans (Adults)	Nausea, vomiting, diarrhea, skin rash from contact.	Low	Accidental ingestion is rare; risk is primarily from large amounts or skin contact.
Children	Nausea, vomiting, diarrhea.	Moderate	Higher risk due to curiosity; more vulnerable to smaller amounts.
Dogs & Cats	Vomiting, diarrhea, lethargy, loss of appetite.	Moderate to High	Curious pets often chew on plants; smaller animals are more susceptible.
Livestock (Horses)	Vomiting, diarrhea, depression.	High	Larger grazing animals consume higher quantities, increasing the potential for more severe issues.

How to Handle Suspected Hydrangea Poisoning

Taking swift action is crucial if you believe a person or pet has ingested hydrangea. Here are the recommended steps:

Immediate Action: Remove any remaining plant material from the mouth or immediate area.
For Humans: Contact your local poison control center immediately for guidance. If severe symptoms like difficulty breathing or loss of consciousness occur, call 911.
For Pets: Call your veterinarian, a 24-hour emergency veterinary clinic, or a pet poison control hotline immediately. Take a sample of the plant with you to help with identification.
Do Not Induce Vomiting: Never induce vomiting unless directed to do so by a medical or veterinary professional, as it can sometimes cause more harm.
Supportive Care: Treatment for poisoning is often supportive, focusing on managing symptoms. Your vet may recommend fluid therapy for dehydration or medication to ease gastrointestinal discomfort.

Preventing Hydrangea Exposure

The best way to manage the risk of hydrangea toxicity is through prevention, especially in households with pets and young children. Here are some effective strategies:

Mindful Planting: Place hydrangeas in areas that are not easily accessible to pets and children, such as in fenced-off zones or raised garden beds.
Physical Barriers: Use decorative fencing or other physical barriers to keep curious animals away from the plants.
Supervision: Always supervise pets and small children when they are playing or exploring in the garden.
Gardening with Care: When handling hydrangeas, especially the sap, use gloves to protect your skin from potential contact dermatitis.
Safe Alternatives: For peace of mind, consider planting pet-friendly alternatives like rosemary or bromeliads, as suggested by sources like Kinship.
Keep Indoors Safe: Remember that dried hydrangea bouquets and floral arrangements are still toxic and should be kept out of reach of pets.

Conclusion

While the beautiful hydrangea is a popular fixture in many gardens, the answer to the question 'Are hydrangeas toxic?' is a definitive yes. The plant contains cyanogenic glycosides, which can cause gastrointestinal distress in both humans and pets if ingested. While severe poisoning is rare, it is a serious risk that should not be overlooked. By understanding the potential dangers, recognizing the symptoms of ingestion, and taking proactive steps to prevent exposure, you can enjoy the aesthetic benefits of hydrangeas while ensuring the safety of your family and pets. For additional guidance on safe gardening practices, resources like the ASPCA Poison Control Center can provide valuable information on toxic and non-toxic plants.

Frequently Asked Questions

Yes, hydrangeas are toxic to dogs. They contain cyanogenic glycosides that, if ingested, can cause vomiting, diarrhea, lethargy, and depression. Although severe poisoning is rare, you should contact your veterinarian if you suspect your dog has eaten any part of the plant.

Yes, hydrangeas are poisonous to cats. Chewing or ingesting the leaves, flowers, or buds can cause gastrointestinal upset, lethargy, depression, and other signs of illness. Contact your vet immediately if your cat eats a hydrangea.

Yes, hydrangeas are toxic to humans, particularly if ingested by curious children. Ingestion can cause stomach pain, vomiting, and diarrhea. In severe cases, large amounts could potentially lead to more serious issues.

All parts of the hydrangea plant are toxic, including the flowers, leaves, buds, and bark. The toxins are released when the plant material is chewed or crushed.

Yes, handling hydrangeas can cause contact dermatitis, a type of skin rash, in sensitive individuals. The sap of the plant is responsible for this reaction, which can result in redness, itching, and hives.

Yes, dried hydrangeas are just as poisonous as fresh ones, if not more so, because the toxic cyanogenic glycoside compounds become concentrated. It's important to keep dried arrangements out of reach of pets.

If your dog eats a hydrangea, remove any remaining plant matter, then immediately call your veterinarian or a pet poison control hotline. Monitor your dog for symptoms and gather information about the amount consumed and when it happened.

Common symptoms include vomiting, diarrhea, lethargy, depression, and loss of appetite. If you see more serious signs like breathing problems, seizures, or collapse, seek emergency veterinary care immediately.