Are Periwinkle Plants Poisonous?

Human Poisoning

• All parts of Madagascar periwinkle are poisonous if ingested or smoked, causing hallucinations. According to the North Carolina State University Extension, the plant causes only low toxicity if eaten. The University of Arkansas Cooperative Extension Service classifies lesser periwinkle as a Toxicity Category 1 plant, capable of causing systemic toxicity with symptoms ranging from mild abdominal cramping to heart complications. Floridata warns that even under the supervision of a doctor, products containing Madagascar periwinkle can cause undesirable side effects.

Pet Poisoning

• The American Society for the Prevention of Cruelty to Animals lists Madagascar periwinkle as being toxic to dogs, cats and horses, causing symptoms such as vomiting, diarrhea, low blood pressure and depression. Serious poisoning cases may lead to seizures and coma. Pets may shake and have difficulty walking, but death is a rare outcome, according to the Pet Poison Helpline. Animals usually find big periwinkle and similar plants unpalatable and are thus unlikely to eat enough to cause paralysis or death.

Treatment

• If you or someone you know has ingested periwinkle, call your doctor or contact the American Association of Poison Control Centers by calling the free Poison Help Line at 1-800-222-1222. If your pet has ingested periwinkle, remove any leftover plant matter from your pet's mouth and call your veterinarian or the ASPCA Animal Poison Control Center at 888-426-4435. The ASPCA may charge a consultation fee. Provide plenty of water for your pet, as vomiting and diarrhea cause dehydration.

Culture

• Periwinkles are safe to grow as long as they are kept away from children and pets. Madagascar periwinkle may be grown in U.S. Department of Agriculture zones 9 to 11, while lesser periwinkle prefers the cooler weather in USDA zones 4 to 8. Big periwinkle grows best in USDA zones 7 to 9 and is invasive in some locations. Periwinkles are known for their shade tolerance, though they may also be grown in sunny sites. Growth will be especially fast in well-draining, moist soil.