Box elder Toxic?

Updated 2026-03-06| 4 min read| 3,747 found this helpful

Toxic compounds include hypoglycin A (in seeds/seedlings) and mycotoxins from Rhytisma acerinum fungus

Primary toxicity risk affects horses, with a 75% fatality rate within 72 hours of symptom onset

Exposure risk is highest in spring and autumn when toxic plant debris accumulates on pastures

FAQ

Is Box elder toxic to Humans?

No confirmed toxicity symptoms reported in available clinical data (Non-toxic)

Is Box elder toxic to Cats?

No confirmed toxicity symptoms reported in available clinical data (Non-toxic)

Is Box elder toxic to Dogs?

No confirmed toxicity symptoms reported in available clinical data (Non-toxic)

Is Box elder toxic to Horses?

Atypical/seasonal pasture myopathy with muscle weakness, stiffness, dark urine, frequent lying down, colic signs, muscle tremors, and severe muscle pain (Severe)

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Toxicity Details

Humans

Non-toxic

No confirmed toxicity symptoms reported in available clinical data

Cats

Non-toxic

No confirmed toxicity symptoms reported in available clinical data

Dogs

Non-toxic

No confirmed toxicity symptoms reported in available clinical data

Horses

Severe

Atypical/seasonal pasture myopathy with muscle weakness, stiffness, dark urine, frequent lying down, colic signs, muscle tremors, and severe muscle pain

Toxicity Snapshot

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

Exposure RouteIngestion of toxic plant parts, most commonly by horses grazing on contaminated pastures

Toxic CompoundsHypoglycin A (non-proteinogenic amino acid found in seeds and seedlings); Mycotoxins from Rhytisma acerinum (maple tar spot fungus); Potential associated toxins from Clostridium sordellii bacteria

First Aid & Prevention

First 30 Minutes

• Immediately move exposed animals (especially horses) away from access to box elder plant material
• Provide uncontaminated hay and fresh water to conscious, alert horses to reduce further ingestion risk
• Collect samples of any suspected ingested plant material to share with veterinary staff for identification

Contact Vet Immediately

• Any confirmed or suspected ingestion of box elder seeds, seedlings, or spotted leaves by horses
• Observation of muscle weakness, dark urine, colic, tremors, or unusual lethargy in horses grazing near maple trees
• Unusual gastrointestinal or neurological symptoms in companion animals following suspected exposure

Prevention

• Limit horse pasture time to under 6 hours during high-risk periods (spring, October to December autumn)
• Avoid grazing horses on pastures containing box elder or other maple trees, fallen wood, or accumulated foliage
• Provide adequate supplementary hay for horses on overgrazed pastures to reduce accidental ingestion of toxic plant material

Treatment & Prognosis

• Administer veterinary-directed decontamination (e.g. activated charcoal) to reduce toxin absorption
• Provide supportive symptomatic care including fluid therapy, pain management, and muscle support
• Monitor muscle and kidney function for at least 72 hours post-exposure to catch secondary complications early

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Professional Toxicology

Scientific NameAcer negundo L.

AliasesBoxelder maple、Ash-leaved Maple、Maple ash、Ashleaf maple、Eschen-Ahorn (German)、Acero americano (Italian)、Erable à feuilles de frêne (French)

Toxicity Grade

HumansNon-toxic

CatsNon-toxic

DogsNon-toxic

HorsesSevere

Target Organs

Skeletal musclesKidneys (secondary to myoglobin release from damaged muscle)

Mechanism of Action

• Hypoglycin A disrupts fatty acid oxidation and energy production in muscle cells, leading to widespread muscle tissue breakdown

• Associated mycotoxins and Clostridium sordellii may exacerbate toxic effects and increase disease severity

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Horse: High risk of fatal atypical pasture myopathy; 75% of affected animals die within 72 hours of symptom onset

Cat: No confirmed toxicity cases reported in available clinical data

Dog: No confirmed toxicity cases reported in available clinical data

Confusion Risk

The following plants look similar and may be confused:

Sycamore maple Acer pseudoplatanus

Closely related maple species that also contains hypoglycin A and causes identical horse toxicity; visually similar foliage and habitat to box elder

Japanese maple Acer palmatum

Related ornamental maple that may also contain hypoglycin A; differentiated by its smaller, more deeply lobed decorative foliage

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Related Toxic Plants

Ohio buckeye

Aesculus glabra

Moderate to high toxicity to humans, livestock, and companion animals, causing neurological and gastrointestinal symptoms

Horse chestnut

Aesculus hippocastanum

Moderate toxicity, causing gastrointestinal distress, muscle weakness, and paralysis if ingested in large quantities

Golden rain tree

Koelreuteria paniculata

Low to moderate toxicity, causing gastrointestinal irritation and central nervous system depression in humans and animals

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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.