Introduction to Toxic Cacti and Lookalikes
Many people assume all cacti are safe, or at least benign beyond their spines. However, this is a dangerous misconception. The world of succulent plants includes a variety of species that are toxic if ingested, or whose sap can cause serious harm upon contact. A critical point is that some of the most dangerous plants that look like cacti are not true cacti at all, but belong to a different family entirely. This article will detail what cactus should you not eat, focusing on genuinely toxic species and common, poisonous lookalikes, to ensure your safety and the safety of your pets.
Cacti Containing Hallucinogenic Alkaloids
Some of the most notorious non-edible cacti are those known for their psychoactive properties. These plants contain mescaline, a hallucinogenic alkaloid, which is toxic if consumed.
Peyote (Lophophora williamsii)
Peyote is a small, spineless cactus with a rounded, grayish-green body. It is native to northern Mexico and the southwestern United States.
- Why you shouldn't eat it: Peyote contains mescaline, which causes vivid, and sometimes frightening, hallucinations. Ingestion can lead to severe nausea, vomiting, and a rapid increase in heart rate and blood pressure. Outside of specific ceremonial use by members of the Native American Church, consumption is illegal and medically unsafe.
San Pedro Cactus (Echinopsis pachanoi)
This is a tall, columnar cactus with fewer spines than many others. It is often grown as an ornamental plant.
- Why you shouldn't eat it: Similar to Peyote, the San Pedro cactus contains mescaline and other alkaloids. Ingestion is known to cause severe gastrointestinal distress and powerful hallucinogenic effects, which can last for many hours. It should be kept strictly ornamental and out of reach of children and pets.
The Deceptive Lookalikes: Toxic Euphorbias
Perhaps the most dangerous and common mistake is confusing a true cactus with a species from the Euphorbia genus. While these plants often have a succulent, spiny appearance, they are not true cacti and are highly toxic.
Pencil Cactus (Euphorbia tirucalli)
Also known as the Firestick succulent, this plant has thin, branching stems that resemble pencils.
- Why you shouldn't eat it: The Pencil Cactus produces a milky white sap, or latex, that is highly toxic. Contact with skin can cause a painful, burning rash, and exposure to the eyes can lead to temporary blindness. If ingested, it can cause severe gastrointestinal and internal issues.
African Milk Tree (Euphorbia trigona)
This plant has distinct, three-sided stems with small leaves and spines along the edges.
- Why you shouldn't eat it: The African Milk Tree also contains the same irritating and toxic milky sap found in other Euphorbias. Care should be taken during pruning or handling to avoid skin and eye contact.
Other Risky Cacti and Succulents
Barrel Cactus (Ferocactus and Echinocactus species)
While some desert survival guides mention the possibility of drinking water from a barrel cactus, this is extremely ill-advised.
- Why you shouldn't eat it: The flesh of a barrel cactus is typically highly acidic and contains alkaloids. Ingesting it can cause severe diarrhea, vomiting, and other gastrointestinal distress, which would only worsen a dehydration situation.
Cholla Cactus (Cylindropuntia species)
The fruit of some cholla species can be consumed after careful preparation, but the plant's spines pose a significant danger.
- Why you shouldn't eat it: The main risk is not from poison, but from the viciously barbed spines and tiny, almost invisible glochids that can easily lodge in the skin and mouth, causing pain and irritation. Some species of cholla have also been reported to be toxic to the kidneys.
Comparison of Toxic and Edible Species
| Species | Family | Toxicity Level | Key Identifying Feature |
|---|---|---|---|
| Peyote | Cactaceae | High (Mescaline) | Spineless, flattened buttons with wooly tufts |
| San Pedro | Cactaceae | High (Mescaline) | Tall, columnar growth with few spines |
| Pencil Cactus | Euphorbiaceae | High (Toxic Sap) | Branching, cylindrical, and leafless stems |
| African Milk Tree | Euphorbiaceae | High (Toxic Sap) | Three-sided, ribbed stems with spines and leaves |
| Barrel Cactus | Cactaceae | Moderate (Acidic Flesh) | Large, round or cylindrical body with large spines |
| Prickly Pear | Cactaceae | Low (Glochids) | Flat, pad-like segments; fruit and pads edible after careful preparation |
Safe Handling and What to Do in an Emergency
If you own cacti or suspect you have a toxic lookalike, proper handling and caution are essential, especially with pets and children in the home.
- Wear protective gear: Always wear thick gloves and eye protection when handling or pruning any unknown cacti or succulents, especially those with milky sap.
- Identify your plants: Purchase plants from reputable nurseries and know the species. If you are unsure, do not handle or consume any part of the plant.
- Keep pets and children away: Place potentially toxic plants out of reach. If you see signs of ingestion like vomiting or drooling in a pet, contact a veterinarian immediately.
- What to do if exposed to toxic sap: If you get milky sap on your skin or in your eyes, rinse the area thoroughly with water immediately. Follow up with soap for the skin. Seek medical attention if irritation persists or if eyes were exposed.
- What to do if you suspect ingestion: If a person or pet ingests a potentially toxic cactus, contact your local poison control center or a veterinarian immediately. Do not induce vomiting unless instructed by a medical professional.
Conclusion
The most important takeaway is to exercise caution and avoid consuming any cactus or succulent unless you are 100% certain of its safety. The primary dangers come from species containing potent hallucinogenic alkaloids, toxic lookalikes from the Euphorbia genus with irritating sap, and even edible-but-risky plants with hazardous spines. Proper identification and safe handling are key to enjoying these fascinating plants without risking your health. When in doubt, simply don't eat it.
