Cats & Dogs
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.
Sources
Pet safety reference
Smooth Hydrangea
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
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.
Dogs — concern notes
Common signs
Vomiting, diarrhea, increased heart rate, and potential depression.
Escalation note
While usually mild, ingestion can cause significant digestive irritation. Always consult a veterinarian if your dog shows signs of illness after exposure.
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
ASPCA Toxic Plant List
toxicology · 99% reliability
Hydrangea arborescens is listed as toxic to both cats and dogs due to the presence of cyanogenic glycosides.
NC State Extension Plant Toolbox
botanical · 94% reliability
Hydrangea arborescens is a native shrub that is toxic if ingested by humans and pets.
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.
Is smooth hydrangea toxic to dogs?
Yes, smooth hydrangea (Hydrangea arborescens) is toxic to dogs. It contains cyanogenic glycosides that can cause vomiting, diarrhea, increased heart rate, and depression. Ingestion typically causes mild-to-moderate digestive irritation, though large doses carry a small risk of more serious effects.
What symptoms will my dog show after eating hydrangea?
The most common signs are vomiting, diarrhea, and lethargy or withdrawal. Your dog may also drool or show mild abdominal discomfort. In rare cases involving a large ingestion, watch for bright red gums, panting, or collapse — these can signal a cyanide-type effect and require immediate emergency care.
What should I do if my dog ate smooth hydrangea?
Call your vet or the ASPCA Animal Poison Control Center at (888) 426-4435 right away. Cyanide-type signs can appear within 15–20 minutes of a large ingestion, so don't wait to see if symptoms develop. For mild GI upset, contact your vet if vomiting or diarrhea persists beyond a few hours or your dog cannot keep water down.
When is hydrangea poisoning in dogs a medical emergency?
Seek emergency care immediately if you notice weakness, bright red gums, panting, or rapid breathing — those signs can indicate a cyanide effect after a heavy dose. Routine vomiting and diarrhea are more common and usually self-limiting, but call your vet if symptoms persist or your dog seems unable to stay hydrated.
Same safety verdict
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