Are Hydrangeas Poisonous to Dogs?

The toxic compound in hydrangeas:

• Cyanogenic glycoside (cyanide-containing compounds present in leaves, flowers, buds, and other plant parts; chewing or damaging the plant can release free cyanide)

If your dog ate hydrangeas, watch for:

• •Vomiting
• •Diarrhea
• •Depression/lethargy
• •Drooling
• •In rare, severe cyanide intoxication: gasping/labored breathing, collapse, seizures, and death

Are hydrangeas poisonous to dogs?

Yes. The ASPCA lists hydrangea as toxic to dogs (as well as cats and horses). The toxic component is a cyanogenic glycoside found throughout the plant. In practice, ingestion most often causes gastrointestinal upset such as vomiting, diarrhea, and depression rather than full cyanide poisoning.

Which parts of the hydrangea are toxic, and how much is dangerous?

All parts of the plant contain cyanogenic compounds, including leaves, flowers, and buds. According to Pet Poison Helpline, the amount needed to cause serious cyanide poisoning is large, so true cyanide toxicity is uncommon in dogs and more often seen in livestock. However, even small amounts can cause vomiting and diarrhea, so any ingestion should be taken seriously and a vet or poison hotline contacted.

What should I watch for if my dog ate a hydrangea?

Watch for vomiting, diarrhea, drooling, and lethargy/depression. In rare severe cases, signs of cyanide poisoning such as gasping or labored breathing, collapse, or seizures can occur. Because severity depends on the amount eaten and the dog's size, contact your veterinarian, the ASPCA Animal Poison Control Center (888-426-4435), or Pet Poison Helpline (855-764-7661) promptly.

• ASPCA - Toxic and Non-toxic Plants: Hydrangea
• Pet Poison Helpline - Hydrangea

Last updated 2026-06-25