Bigleaf hydrangea Toxic?

Updated 2026-03-06| 2 min read| 1,428 found this helpful

All parts of the bigleaf hydrangea plant contain toxic compounds including cyanogenic glycosides, terpenes, and dihydroisocoumarins.

Ingestion typically causes only mild, self-limiting gastrointestinal symptoms in humans and most animal species.

Severe systemic poisoning is extremely rare, as the concentration of toxic cyanide-producing compounds is very low in the plant.

FAQ

Is Bigleaf hydrangea toxic to Humans?

May cause hypersalivation, nausea, vomiting, diarrhea, and mild abdominal pain; severe toxicity is not documented from typical small ingestions. (Low)

Is Bigleaf hydrangea toxic to Cats?

Hypersalivation, vomiting, diarrhea (Low)

Is Bigleaf hydrangea toxic to Dogs?

Hypersalivation, vomiting, diarrhea (Low)

Is Bigleaf hydrangea toxic to Horses?

No specific clinical symptoms documented; mild gastrointestinal distress including salivation and loose stool is possible if large amounts are ingested. (Low)

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Toxicity Details

Humans

Low

May cause hypersalivation, nausea, vomiting, diarrhea, and mild abdominal pain; severe toxicity is not documented from typical small ingestions.

Cats

Low

Hypersalivation, vomiting, diarrhea

Dogs

Low

Hypersalivation, vomiting, diarrhea

Horses

Low

No specific clinical symptoms documented; mild gastrointestinal distress including salivation and loose stool is possible if large amounts are ingested.

Toxicity Snapshot

Toxic PartsAll parts of the plant are toxic

Exposure RoutePrimary exposure is ingestion of plant material; contact with raw sap may cause mild skin irritation in sensitive individuals.

Toxic CompoundsCyanogenic glycosides: Taxiphyllin, Hydracyanoside A, (2R)-2-β-D-glucopyranosyloxy-2-(3,4-dimethoxyphenyl)acetonitrile, (2R)-2-[α-D-glucopyranosyl(1→6)β-D-glucopyranosyloxy]-2-(3-hydroxy-4-methoxyphenyl)acetonitrile; Terpenes: Betulinic acid, Hopan-6, Hydrangine A-C, Zeroin, and related derivatives; Dihydroisocoumarins: Hydrangenol, Hydrangenol-4'-O-beta-D-glucopyranoside

First Aid & Prevention

First 30 Minutes

• Remove any remaining plant material from the mouth of the affected person or animal immediately.
• Rinse the mouth thoroughly with cool clean water to remove residual plant particles or sap.
• Offer small sips of water to dilute irritants; do not induce vomiting unless explicitly directed by a medical or veterinary professional.

Contact Vet Immediately

• Vomiting or diarrhea persists for more than 2 hours after ingestion.
• Affected individual shows signs of lethargy, loss of appetite, or unusual behavioral changes post-exposure.
• Large quantities of plant material are ingested by small children, small pets, or small livestock.

Prevention

• Keep potted hydrangeas out of reach of young children, cats, and small dogs.
• Label garden hydrangea plants to avoid accidental ingestion during gardening or foraging activities.
• Wear disposable gloves when pruning hydrangeas to avoid mild skin irritation from sap contact.

Treatment & Prognosis

• Supportive care including fluid therapy and anti-emetic medication to control vomiting and prevent dehydration.
• Activated charcoal may be administered within 1 hour of large ingestions to bind remaining toxic compounds.
• No specific antidote exists; symptoms typically resolve fully within 24 to 48 hours with appropriate supportive care.

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Professional Toxicology

Scientific NameHydrangea macrophylla (Thunb.) Ser.; Hortensia opuloides Lam.; Hydrangea hortensia Siebold; Hydrangea macrophylla subsp. macrophylla (Thunb.) Ser.; Hydrangea opuloides (Lam.) K. Koch; Viburnum macrophyllum Thunb.

AliasesFrench hydrangea、Lacecap hydrangea、Mophead hydrangea、Garden hydrangea、Farmer's hydrangea、Ball hydrangea、Plate hydrangea、Japanese hydrangea、Large-leaf hortensia、Ortensia

Toxicity Grade

HumansLow

CatsLow

DogsLow

HorsesLow

Target Organs

Gastrointestinal tract (mouth, esophagus, stomach, intestines)

Mechanism of Action

• Cyanogenic glycosides break down in the digestive tract to release small amounts of cyanide that irritate gastrointestinal mucosal linings.

• Terpene and dihydroisocoumarin compounds contribute to local inflammatory effects on the gut lining.

• Systemic cyanide toxicity does not occur under normal exposure conditions due to very low concentration of glycosides in the plant.

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Goat: Ingestion causes hypersalivation, loss of appetite, and lethargy.

Confusion Risk

The following plants look similar and may be confused:

Other hydrangea species Hydrangea spp.

Visually similar in leaf and flower morphology; most other Hydrangea species have similar low toxicity profiles to bigleaf hydrangea.

Jungle geranium Ixora coccinea

Has similar rounded clustered flower heads; Ixora coccinea is non-toxic, and can be distinguished by its smaller, glossy narrow leaves compared to hydrangea's broad matte leaves.

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Related Toxic Plants

Oakleaf hydrangea

Hydrangea quercifolia

Low toxicity, causes mild gastrointestinal distress if ingested

Climbing hydrangea

Hydrangea anomala subsp. petiolaris

Low toxicity, contains same cyanogenic glycoside compounds as bigleaf hydrangea

Smooth hydrangea

Hydrangea arborescens

Low toxicity, same symptom profile as bigleaf hydrangea following ingestion

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Data Sources

1. CliniTox (Universität Zürich)

This information is for reference only and does not constitute medical advice. If ingestion or poisoning is suspected, seek medical or veterinary attention immediately.