Is Madagascar Periwinkle Poisonous? Toxicity Guide for Pets and People

Madagascar periwinkle is toxic to dogs, cats, horses, and humans. The plant (Catharanthus roseus, formerly classified as Vinca rosea) is a popular garden annual prized for its bright flowers in pink, white, red, and purple. Despite its cheerful appearance and widespread use as bedding and container plant, every part contains vinca alkaloids that are toxic to the nervous system and heart. Any ingestion by a pet or child warrants contact with a vet or poison control.

Why Madagascar Periwinkle Is Toxic

The plant contains over 100 identified alkaloids, including vinblastine and vincristine, which are derived from this species and used in chemotherapy drugs. These alkaloids disrupt cell division and affect nerve function. In the context of poisoning (as opposed to controlled therapeutic use), they depress the central nervous system, lower blood pressure, and at high doses can cause seizures, coma, and death.

Madagascar periwinkle should not be confused with common periwinkle (Vinca minor or Vinca major), which is a different but closely related plant that shares similar toxicity. Both are members of the Apocynaceae family and both should be kept away from pets and children.

What Part of Madagascar Periwinkle Is Toxic?

All parts of the plant are toxic. There are no safe portions to consume.

• Leaves are the most commonly ingested part, as they are available throughout the growing season.
• Flowers are toxic.
• Stems contain alkaloids throughout.
• Seeds are toxic.
• Roots are toxic.

Symptoms of Madagascar Periwinkle Ingestion

Symptoms can range from mild gastrointestinal distress to life-threatening systemic effects depending on the amount ingested.

Dogs and cats: Vomiting and diarrhea are typically the first signs. Low blood pressure causes weakness and unsteadiness. Depression and lethargy follow. With more significant ingestion, tremors, seizures, coma, and death have been reported. Cats are highly sensitive to many alkaloids and may show severe effects from smaller exposures.

Horses: Horses that graze on Madagascar periwinkle can develop serious toxicity. The nervous system and cardiovascular effects are similar: weakness, incoordination, low blood pressure, and in severe cases, collapse.

Humans and children: Nausea, vomiting, and abdominal pain are the primary symptoms from ingestion. The plant’s alkaloids are irritating to mucous membranes. In children, even relatively small exposures should prompt a call to poison control because of their lower body weight and the potency of the compounds.

What to Do If Someone Ingests Madagascar Periwinkle

1. Remove any remaining plant material from the mouth.
2. Do not induce vomiting unless directed by a vet or poison control professional.
3. Call poison control at 1-800-222-1222 (US) or your vet immediately.
4. If your pet is already showing signs of weakness, tremors, or difficulty breathing, go directly to an emergency vet.
5. Bring a sample or clear photo of the plant if you are unsure of the exact species.

Treatment is supportive. There is no specific antidote for vinca alkaloid poisoning. Decontamination, IV fluids, and monitoring of heart rate and blood pressure are the core of veterinary and medical management.

Safe Handling Around Pets and Children

• Do not plant Madagascar periwinkle in outdoor spaces where dogs have unsupervised access.
• Choose pet-safe annuals such as marigolds, zinnias, or snapdragons for beds shared with dogs and cats.
• When deadheading or handling the plant, wear gloves and wash hands afterward.
• Keep potted Madagascar periwinkle on high surfaces out of reach of pets and young children.
• Dispose of pruned material in a sealed bin; do not leave clippings on the ground where a dog might chew them.
• Be aware that plants sold under names like “vinca,” “annual vinca,” or “periwinkle” at garden centers are usually Catharanthus roseus and carry the same toxicity.

Frequently Asked Questions

Is Madagascar periwinkle the same as vinca? At garden centers, plants sold as “annual vinca” or simply “vinca” are almost always Catharanthus roseus (Madagascar periwinkle). The name is used interchangeably in horticulture. True Vinca (Vinca minor, Vinca major) is the trailing ground cover, which is also toxic. The toxicity profiles are similar for both.

My dog ate some Madagascar periwinkle flowers. How serious is this? Call your vet right away. The amount ingested and your dog’s body weight will determine how urgent the response needs to be. Do not wait for symptoms to appear before making contact.

Can Madagascar periwinkle cause death in pets? Yes, in significant ingestion cases. The ASPCA lists coma and death among the possible outcomes. Most accidental exposures from nibbling a few leaves do not result in death, but any ingestion should be taken seriously and evaluated by a vet.

Is Madagascar periwinkle toxic to touch? The primary risk is from ingestion. Skin contact with sap may cause mild irritation in sensitive individuals, but it does not cause systemic toxicity through the skin. Wash hands after handling the plant.

Are the seeds of Madagascar periwinkle toxic? Yes. All parts of the plant are toxic, including the seeds. Keep seed packets and seedlings out of reach of pets during the planting season.