Are Hydrangeas Poisonous to Cats?

Hydrangeas are prized for their colorful blooms, but these flowering shrubs can make cats sick if they nibble on any part of the plant. While some hydrangea varieties are more toxic than others, each has the potential to poison cats. Here's how to keep your kitty safe and protected.

Why Are Hydrangeas Poisonous to Cats?

Hydrangeas contain chemicals called cyanogenic glycosides, which can be toxic to cats and other animals (including humans). When the plant is chewed or ingested, the chemical is released and can cause a variety of symptoms such as 

vomiting, diarrhea, and lethargy.1

Cyanogenic glycoside is a type of compound that can release cyanide when it comes into contact with certain enzymes in the digestive system. While the level of toxicity varies depending on the specific species of hydrangea and the amount ingested, it's important to note that any amount of cyanide can be dangerous to cats.2

There are over 75 types of hydrangeas, and all contain toxins that can be harmful to cats if ingested in large quantities. However, the type of hydrangea that is most toxic to cats is the Bigleaf hydrangea (Hydrangea macrophylla). This plant contains a substance which can cause vomiting, diarrhea, and lethargy in cats if consumed in large quantities. The flowers of the Bigleaf hydrangea also contain a higher concentration of the toxin than the leaves or stems.3

While some types of hydrangeas may be more toxic than others, any type of plant can be dangerous to cats if ingested in large quantities. If you suspect that your cat has ingested any part of a hydrangea or any other plant, seek veterinary attention immediately.

Signs of Hydrangea Poisoning in Cats

The signs of hydrangea poisoning in cats can vary depending on the amount ingested and the severity of the toxicity. Some signs of poisoning include:

• Vomiting
• Diarrhea
• Loss of appetite
• Lethargy, weakness, or depression
• Drooling
• Difficulty breathing
• Seizures
• Pale or blue gums
• Rapid heart rate