Rex Begonia Toxic?

Updated 2026-03-06| 3 min read| 2,554 found this helpful

Rex Begonia is confirmed toxic to cats, dogs, and horses per ASPCA toxicology data

Its primary toxic component is soluble calcium oxalates, with highest toxicity in underground plant parts

Ingestion can cause severe effects including life-threatening kidney failure in grazing animals like horses

FAQ

Is Rex Begonia toxic to Humans?

No formal human toxicity data is documented, but accidental ingestion may cause oral irritation, vomiting and mild digestive upset as a general precaution (Low)

Is Rex Begonia toxic to Cats?

Vomiting, excessive salivation, oral pain and gastrointestinal distress (Moderate)

Is Rex Begonia toxic to Dogs?

Vomiting, excessive salivation, oral irritation and gastrointestinal upset (Moderate)

Is Rex Begonia toxic to Horses?

Kidney failure (especially with large ingestion volumes), salivation, vomiting and general digestive distress (High)

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Toxicity Details

Humans

Low

No formal human toxicity data is documented, but accidental ingestion may cause oral irritation, vomiting and mild digestive upset as a general precaution

Cats

Moderate

Vomiting, excessive salivation, oral pain and gastrointestinal distress

Dogs

Moderate

Vomiting, excessive salivation, oral irritation and gastrointestinal upset

Horses

High

Kidney failure (especially with large ingestion volumes), salivation, vomiting and general digestive distress

Toxicity Snapshot

Toxic PartsUnderground plant parts (highest toxicity); all other plant parts carry minor to moderate ingestion toxicity risk

Exposure RoutePrimary exposure route is ingestion; direct skin contact may cause mild transient irritation in sensitive individuals

Toxic CompoundsSoluble calcium oxalates

First Aid & Prevention

First 30 Minutes

• Remove any remaining plant material from the exposed individual/pet's mouth and rinse thoroughly with clean, cool water
• Prevent further access to the Rex Begonia plant and collect a sample of the ingested part for medical/veterinary reference
• Do not induce vomiting unless explicitly instructed to do so by a licensed medical provider or veterinarian

Contact Vet Immediately

• The animal has ingested any quantity of Rex Begonia, particularly the underground root/tuber parts
• The animal exhibits visible symptoms including vomiting, excessive salivation, lethargy or loss of appetite post-exposure
• A horse or other grazing livestock has had access to or ingested the plant

Prevention

• Place potted Rex Begonias out of reach of pets, small children and grazing livestock
• Clearly label Rex Begonia plants to alert caretakers and visitors of their toxicity risk
• Remove wild-growing Rex Begonias from horse pastures and other livestock grazing areas to avoid accidental ingestion

Treatment & Prognosis

• Supportive care including fluid therapy to reduce kidney damage risk, especially for grazing animals like horses
• Symptomatic care to manage vomiting, oral pain and gastrointestinal irritation in cats and dogs
• Kidney function monitoring for 24 to 72 hours post-ingestion for horses and other grazing species

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Professional Toxicology

Scientific NameBegonia rex

AliasesKing Begonia、Painted Leaf Begonia、Rex Cultorum Begonia

Toxicity Grade

HumansLow

CatsModerate

DogsModerate

HorsesHigh

Target Organs

KidneysOral mucosaGastrointestinal tract

Mechanism of Action

• Soluble calcium oxalates are absorbed post-ingestion, binding to bodily calcium and accumulating in renal tissue to cause kidney damage, while also triggering local irritation of oral and digestive tract mucosal membranes

Other Species Risk (CliniTox)

Information from CliniTox veterinary text.

Cattle: High risk of kidney injury and failure if large quantities are ingested during grazing

Sheep: Moderate toxicity, ingestion may cause digestive upset and potential kidney damage with high exposure levels

Domestic Rabbits: Low to moderate toxicity, ingestion typically causes oral irritation and mild to moderate gastrointestinal distress

Confusion Risk

The following plants look similar and may be confused:

Polka Dot Begonia Begonia maculata

Visually similar due to decorative variegated foliage; key difference is Polka Dot Begonia has distinct uniform white spots on leaves, while Rex Begonia has iridescent multi-tonal marbling; both carry similar calcium oxalate toxicity

Fancy Leaf Caladium Caladium bicolor

Often confused for its large, brightly patterned leaves; Caladium has distinct heart-shaped foliage with bold red/pink veining, and also contains toxic calcium oxalate crystals

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Related Toxic Plants

Tuberous Begonia

Begonia × tuberhybrida

Moderate toxicity for cats, dogs and horses, contains soluble calcium oxalates

Wax Begonia

Begonia cucullata

Low to moderate toxicity, highest toxic compound concentrations found in underground roots

Iron Cross Begonia

Begonia masoniana

Moderate toxicity, ingestion triggers salivation, vomiting and digestive upset in pets

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Data Sources

1. ASPCA Animal Poison Control

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