Is Hydrangea Toxic to Cats?

Hydrangea macrophylla

Hydrangea contains cyanogenic glycosides, which release cyanide when the plant tissue is damaged. In practice cats that chew leaves show vomiting, diarrhoea and lethargy; serious poisoning requires a larger amount than a single leaf.

They are a staple of British gardens, and cut hydrangea heads are popular in autumn arrangements indoors.

Which parts are dangerous

• leaves
• flower buds
• bark

What to watch for in the UK

• Garden borders and cut-flower arrangements in late summer.
• Dried hydrangea heads kept indoors stay toxic.
• Fallen leaves in autumn are a common nibble.
• Prunings left on the ground are accessible.

If your cat has already chewed it

1. Phone your vet if a significant amount was chewed.
2. Take a photo and note the part eaten.
3. Watch for vomiting and lethargy.

Take a photo of the plant, and a cutting if you can do it safely — identification is half of the vet's decision. Out of hours, use your practice's emergency number. This page explains risk; it cannot diagnose your cat and it contains no home treatments.

If your cat has vomited after eating a plant, see the cat vomiting guide and, if there is blood, vomiting blood. For a general red-flag checklist, use sick cat symptoms. If the worry is food rather than a plant, the can cats eat guide covers 36 everyday foods.

Related plants

Browse the full UK plant checklist (72 plants).