Sycamore maple Toxic?

Updated 2026-03-06| 5 min read| 2,671 found this helpful

Contains toxic non-proteinogenic amino acid hypoglycin A in its seeds and seedlings that drives core toxicity effects

Exposure in horses causes atypical myopathy with a 75% mortality rate within 72 hours of symptom onset

Easily confused with other Acer (maple) species, many of which carry similar toxicity risks

FAQ

Is Sycamore maple toxic to Humans?

No confirmed toxicity data available for humans; seek medical care if adverse effects occur after ingestion (Unknown)

Is Sycamore maple toxic to Cats?

No confirmed toxicity data available for cats; monitor for unusual symptoms if ingestion is suspected (Unknown)

Is Sycamore maple toxic to Dogs?

No confirmed toxicity data available for dogs; monitor for unusual symptoms if ingestion is suspected (Unknown)

Is Sycamore maple toxic to Horses?

Atypical/seasonal pasture myopathy with muscle weakness/stiffness, dark urine, frequent lying down, colic signs, muscle tremors, and severe muscle pain; 75% of affected horses die within 72 hours (Severe)

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Toxicity Details

Humans

Unknown

No confirmed toxicity data available for humans; seek medical care if adverse effects occur after ingestion

Cats

Unknown

No confirmed toxicity data available for cats; monitor for unusual symptoms if ingestion is suspected

Dogs

Unknown

No confirmed toxicity data available for dogs; monitor for unusual symptoms if ingestion is suspected

Horses

Severe

Atypical/seasonal pasture myopathy with muscle weakness/stiffness, dark urine, frequent lying down, colic signs, muscle tremors, and severe muscle pain; 75% of affected horses die within 72 hours

Toxicity Snapshot

Toxic PartsSeeds, dark discolored seeds, leaves infested with black spot fungal growth (Rhytisma acerinum)

Exposure RouteIngestion of toxic plant parts, most common in grazing horses with access to fallen seeds, seedlings, or infested leaves on pastures

Toxic CompoundsHypoglycin A (non-proteinogenic amino acid); Mycotoxins from Rhytisma acerinum (potential exacerbating factor); Possible associated Clostridium sordellii pathogens

First Aid & Prevention

First 30 Minutes

• Immediately remove the animal from exposure to sycamore maple plant material
• Collect any remaining ingested plant material for formal identification
• Do not induce vomiting unless explicitly instructed to do so by a veterinary professional

Contact Vet Immediately

• Any confirmed or suspected ingestion of sycamore maple parts by horses
• Appearance of muscle weakness, dark urine, colic, or muscle tremors in grazing horses
• Unusual symptoms in any companion animal after suspected exposure to the plant

Prevention

• Limit horse grazing time to under 6 hours during high-risk spring and fall (October to December) periods
• Do not graze horses on pastures containing sycamore maple or other Acer species, accumulated old wood, or fallen leaves
• Provide sufficient hay supplementation for horses on overgrazed pastures to reduce risk of foraging on toxic plant material

Treatment & Prognosis

• Administer appropriate decontamination measures based on exposure level and species
• Provide targeted symptomatic supportive care per standard atypical myopathy emergency therapy protocols
• Monitor muscle enzyme levels, kidney function, and hydration status closely for a minimum of 72 hours post-exposure

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Professional Toxicology

Scientific NameAcer pseudoplatanus L.

AliasesMountain maple、Sycomore maple、False plane tree、Great maple、White maple

Toxicity Grade

HumansUnknown

CatsUnknown

DogsUnknown

HorsesSevere

Target Organs

Skeletal muscleKidneysCardiac muscle

Mechanism of Action

• Hypoglycin A disrupts normal fatty acid oxidation pathways leading to widespread muscle cell damage

• Mycotoxins from Rhytisma acerinum infestations may exacerbate core toxic effects

• Secondary Clostridium sordellii exposure may contribute to worse clinical outcomes in some cases

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Horse: Highest documented risk; ingestion of even small amounts of seeds/seedlings can trigger fatal atypical myopathy, with exposure most common during spring and fall pasturing

Ruminant livestock: No confirmed toxicity reports available; monitor for muscle-related symptoms if exposure to large quantities of plant material occurs

Confusion Risk

The following plants look similar and may be confused:

Other maple species Acer spp.

Nearly identical leaf, bark, and winged seed (samara) structure across most Acer species; many related maples also contain toxic hypoglycin A, making differentiation critical for risk assessment

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Related Toxic Plants

Box elder

Acer negundo

Moderate to severe toxicity, contains hypoglycin A that causes myopathy in horses

Japanese maple

Acer palmatum

Mild to moderate toxicity, contains hypoglycin A with risk for equine myopathy

Ohio buckeye

Aesculus glabra

Moderate to severe toxicity to multiple species, contains neurotoxic aesculin glycosides

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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.