←
Hydrangea
Hydrangea spp.
Hydrangea (Hydrangea spp.) is a popular flowering shrub toxic to cats. It contains cyanogenic glycosides — including hydrangin — primarily in the flower buds and leaves. When metabolised, these compounds release hydrogen cyanide (HCN), although the concentration is typically low enough that serious toxicity requires ingestion of substantial amounts. The plant also contains saponins that contribute to gastrointestinal irritation.
Important Notes
Toxic compounds: cyanogenic glycosides (hydrangin) in flower buds and leaves; saponins throughout the plant
Mechanism: hydrangin yields HCN upon digestion, inhibiting cellular respiration; saponins cause direct GI irritation
Symptoms: vomiting, diarrhea, lethargy, drooling; large ingestion may cause weakness, confusion, and laboured breathing
Flower buds carry the highest cyanogenic concentration — restrict access during blooming
Symptoms are usually mild with minor nibbling; seek veterinary care if large amounts were consumed
Potentially Toxic Parts
Leaf
Entire Plant
Flower
Possible Symptoms Reported in Cats
Respiratory Distress (Dyspnea), Rapid Breathing (Tachypnea), or Seizures
Respiratory · Very Rapid (10–60 minutes after ingestion).
Vomiting
Gastrointestinal · Acute (Clinical signs typically appear quickly, potentially within hours).
Diarrhea
Gastrointestinal · Acute.
Lethargy / Depression / Exhaustion
Neurological · Acute.
Abdominal Pain
Gastrointestinal · Acute.
Disclaimer: This summary was compiled from multiple sources and is for informational use only. It is not a diagnosis or treatment plan. Toxicity can vary based on the substance, amount, plant part, and individual cat. If you think your cat may have been exposed to a toxic substance, contact a veterinarian right away.