Are 4 o'clocks poisonous to humans? Understanding the risks of this common garden plant

September 30, 2025 •

4 min read

According to the North Carolina Extension Gardener Plant Toolbox, the roots and seeds of the four o'clock flower (Mirabilis jalapa) are poisonous to humans, though the severity is generally considered low. This common garden plant poses a potential health risk if ingested, and its toxic parts should be managed with caution.

Quick Summary

The common four o'clock plant (Mirabilis jalapa) is toxic to humans and pets, with its seeds and roots containing poisonous alkaloids. Ingestion can cause gastrointestinal distress, while handling the roots may cause skin irritation.

Key Points

Toxicity: The common four o'clock plant (Mirabilis jalapa) contains toxic compounds in its seeds and roots that are poisonous to humans and pets if ingested.
Ingestion Symptoms: Swallowing the plant's seeds or roots can cause stomach pain, nausea, vomiting, and diarrhea.
Skin Irritation: Handling the tuberous roots can cause contact dermatitis or a rash in some people.
Pet Danger: The plant is also toxic to dogs and cats, causing similar gastrointestinal issues and skin irritation.
Safety Precautions: Wear gloves when handling the plant, keep it away from small children and pets, and promptly clean up any dropped seeds.
Emergency Response: In case of suspected poisoning, immediately contact Poison Control at 1-800-222-1222.

Identifying the Poisonous Parts of the Four O'clock Plant

The four o'clock plant, scientifically known as Mirabilis jalapa and sometimes called Marvel of Peru, is a popular ornamental flower known for its vibrant, fragrant blossoms that open in the late afternoon. Despite its beauty, it is critical to understand that certain parts of the plant are toxic. The primary sources of toxins are the roots and the seeds.

The Toxic Seeds

The seeds are produced in the fall, enclosed in large, dark, spherical, and wrinkled capsules that resemble large peppercorns.
These seeds contain concentrated levels of the toxic compounds and are particularly dangerous to young children and pets who might be tempted to ingest them.
Care should be taken during seed collection, and seeds that have fallen to the ground should be cleared from areas accessible to pets or small children.

The Toxic Roots

The plant grows from a tuberous root, which, like the seeds, contains toxic alkaloids.
In addition to being poisonous if ingested, handling the roots, especially if crushed, can cause contact dermatitis or skin irritation in some individuals.
Gardeners should wear gloves when digging or handling the roots to prevent skin reactions.

Symptoms of Four O'clock Poisoning

The symptoms of four o'clock poisoning in humans are typically gastrointestinal in nature and of low severity, but should still be treated seriously. Ingesting parts of the plant, especially the seeds or roots, can lead to:

Stomach pain and cramps
Nausea
Vomiting
Diarrhea

Contact with the roots or sap can also cause a rash or dermatitis in some individuals. While information on severe human overdose is limited, ingesting large amounts could potentially lead to more serious complications.

First Aid and Emergency Response

If you suspect that a person, child, or pet has ingested parts of a four o'clock plant, you should take immediate action:

For Ingestion: Rinse the mouth with water to remove any remaining plant material. Do not induce vomiting unless instructed to do so by a medical professional.
Call Poison Control: The national Poison Control Center hotline can provide expert guidance. Call them immediately at 1-800-222-1222.
Seek Medical Attention: For severe symptoms or any uncertainty, proceed to a hospital emergency room.
For Skin Contact: If skin irritation or a rash occurs, wash the affected area thoroughly with soap and water.

Comparison of Common Mirabilis Species

Not all plants in the Mirabilis genus have the same level of toxicity. The following table highlights the differences between common species:


Feature	Mirabilis jalapa (Common Four O'clock)	Mirabilis multiflora (Colorado Four O'clock)	Mirabilis expansa (Muaka)
Common Use	Ornamental garden flower	Wildflower, historically used for dyes by Native Americans	Edible root vegetable, food crop in Andean cultures
Toxicity to Humans	Yes, seeds and roots are toxic	Yes, seeds and roots are toxic	No, root and shoots are edible
Toxic Parts	Seeds, roots	Seeds, roots	None (common parts)
Risk Factor	Low to moderate; high for children/pets if seeds are eaten	Low to moderate; found in specific native regions	Edible, low risk

Safe Handling and Prevention

To minimize the health risks posed by four o'clocks in your garden, consider the following preventative measures:

Placement: Plant four o'clocks in areas that are not easily accessible to small children or curious pets.
Gardening Gloves: Always wear gloves when handling four o'clock plants, especially during pruning, weeding, or harvesting seeds, to prevent contact dermatitis from the roots and sap.
Clean Up Seeds: The seeds readily self-seed and can spread. To prevent unwanted growth and limit access for pets or children, collect the dark, ripe seeds from the fading blooms before they drop.
Educate: If you have children, teach them not to put unknown plants or seeds from the garden into their mouths. Similarly, monitor pets to ensure they are not chewing on the plant.
Pet Safety: Ensure pets, particularly puppies and kittens, do not have access to the plants. Ingestion can cause vomiting and diarrhea. If your pet chews on or ingests parts of the plant, contact your veterinarian immediately. For more information on plant risks to pets, resources like the ASPCA provide lists of toxic plants.

Conclusion

Four o'clocks are a beautiful, fragrant, and easy-to-grow addition to many gardens. However, it is essential to be aware that they are poisonous to humans and pets. The seeds and roots contain toxic alkaloids that can cause gastrointestinal distress if ingested and contact dermatitis from handling. By taking simple precautions, such as planting in a safe location and wearing gloves during garden work, you can minimize the risks and safely enjoy the unique beauty of this evening-blooming flower. In the event of suspected poisoning, calling the Poison Control hotline is the most important first step.

Frequently Asked Questions

While the entire plant contains some level of toxicity, the seeds and the tuberous roots of the common four o'clock (Mirabilis jalapa) are the most poisonous parts. Ingestion of these parts poses the highest risk to human and pet health.

Ingestion of four o'clock seeds by a child can lead to symptoms such as stomach pain, vomiting, and diarrhea. You should immediately rinse their mouth with water and call the national Poison Control Center at 1-800-222-1222 for guidance.

Yes, handling the roots of the four o'clock plant can cause contact dermatitis or skin irritation in some people. Wearing gloves is recommended when digging or working with the roots to prevent this reaction.

Yes, four o'clocks are toxic to pets. If a dog or cat ingests parts of the plant, they can experience symptoms like vomiting, diarrhea, and lethargy. Immediate veterinary care is recommended if you suspect your pet has been poisoned.

Four o'clock seeds are found in large, dark, spherical capsules that form after the flowers fade. They have a wrinkled surface and are often described as looking like tiny black peppercorns.

There is no specific antidote for four o'clock poisoning. Treatment focuses on supportive care to manage symptoms, which typically includes monitoring and controlling gastrointestinal issues. The most crucial step is to contact Poison Control immediately for expert advice.

While the common ornamental four o'clock (Mirabilis jalapa) is toxic, some species are edible. For example, Mirabilis expansa, also known as Muaka, is grown as a food crop in some parts of the Andes. However, you should never assume a four o'clock plant is edible unless you are certain of the species and its preparation, and always assume the common garden variety is poisonous.