Cats
Potentially toxicConsulted references classify the plant as toxic or irritating for that pet type.
Verified against ASPCA/provenance audit 2026-05-06 on May 6, 2026.
cat safety reference
Is Smooth Hydrangea safe for cats?
Hydrangea arborescens
Hydrangea arborescens is a deciduous shrub known for its large, rounded clusters of white flowers. It contains cyanogenic glycosides which can cause gastrointestinal distress if ingested by pets.
Hills of SnowHydrangea arborescensSmooth HydrangeaWild Hydrangea
- Light
- Partial shade to full sun
- Habit
- Deciduous shrub
- Care
- Moderate
Safety status
What this means for your cat
Hydrangeas contain cyanogenic glycosides, which sounds frightening but in practice almost always cause stomach upset rather than cyanide poisoning. Cats are more sensitive than dogs because of their smaller body size, but full-blown cyanide signs are rare. Expect vomiting and a quiet, withdrawn cat in most cases.
What to watch for
Most common: vomiting, diarrhea, and depression — your cat retreats and won't engage. Possible: drooling, abdominal discomfort. Rare: signs of cyanide effect, such as bright red gums, panting, or weakness.
Time window
Pet Poison Helpline notes signs of cyanide effect can appear within 15–20 minutes of a large ingestion. The far more common GI upset is usually self-limiting once the plant has cleared the stomach.
When to call the vet
Call immediately if your cat shows weakness, panting, or bright red gums (possible cyanide effect). For mild GI signs, call if vomiting or diarrhea continues past a few hours, especially in kittens or seniors who can dehydrate quickly.
Sources: ASPCA, Pet Poison Helpline.
If a pet has chewed or swallowed plant material and is showing symptoms, contact a veterinarian or poison resource immediately. This product is for structured reference, not diagnosis.
Cats — concern notes
Common signs
Vomiting, diarrhea, lethargy, and potential abdominal pain.
Escalation note
Ingestion can lead to gastrointestinal upset. Please contact your veterinarian or a pet poison control center if you suspect your cat has consumed any part of this plant.
Safer alternatives
No hand-picked alternatives for this plant yet. You can still pick your own using the Compare button on any other plant.
Source evidence
Questions about Smooth Hydrangea
Is smooth hydrangea toxic to cats?
Yes, smooth hydrangea (Hydrangea arborescens) is toxic to cats. It contains cyanogenic glycosides that can cause vomiting, diarrhea, lethargy, and abdominal pain if ingested.
What symptoms will my cat show after eating hydrangea?
The most common signs are vomiting, diarrhea, and depression — your cat may retreat and stop engaging. You may also see drooling and abdominal discomfort. Rarely, a large ingestion can trigger cyanide-related effects: bright red gums, panting, or sudden weakness.
What should I do if my cat ate smooth hydrangea?
Call your vet or the ASPCA Animal Poison Control Center at (888) 426-4435 right away. If your cat shows weakness, panting, or bright red gums, treat it as an emergency and seek care immediately — those signs can appear within 15–20 minutes of a large ingestion. Mild vomiting or diarrhea that continues past a few hours also warrants a call, especially in kittens or senior cats who dehydrate quickly.
What part of the hydrangea plant is poisonous to cats?
The cyanogenic glycosides responsible for toxicity are present throughout the plant. No part of smooth hydrangea is safe for cats to chew or ingest.
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