Plant Parts

All parts of the oleander plant are poisonous due to high levels of cardenolides, also called cardiac glycosides. The ingestion of oleander sap is a common cause of poisoning. The sap is sticky, milky or clear and has an extremely bitter, vile taste. According to Larry J. Thompson, a clinical toxicologist in the College of Veterinary Medicine at Cornell University in Ithaca, New York, the seeds of the oleander are the most poisonous part of the plant, but the sap and all the plant parts are next in line, particularly immature leaves and flowers.

Symptoms of Poisoning

Ingesting any part of the plant will quickly affect the heart, resulting in an irregular heartbeat and eventually death if left untreated. Symptoms may be more difficult to diagnose in animals if they aren’t noticed immediately and treatment is less likely to succeed. Animals may suffer from extreme weakness and seizures. Humans are likely to suffer from gastrointestinal symptoms such as vomiting and diarrhea. Medical treatment will focus on protecting and treating the heart.

Animals

According to the International Oleander Society, the human body should reject even a small amount of the sap, causing vomiting, which could save a person from a more serious reaction, but animals may not experience the same reaction. According to the University of Minnesota Extension’s Horse Program, “.1 percent body weight of leaves may be lethal to a mature horse.” Clear the area around horse pastures of all oleander plants. Any plants in or around where pets play should be removed. Even a few leaves that fall into an ornamental pool from which animals may drink will quickly render it toxic.

Safety

Wash hands and arms thoroughly after handling any part of the oleander plant. Never use any part of the plant as kindling or as fuel for fire, as burning the branches or twigs of the tree will produce a toxic smoke. Never use the branches as skewers and keep in mind that honey from bees that sucked the nectar of oleander is also poisonous. According to "The New York Times," induced vomiting is not recommended unless at the insistence of poison control or a health care professional.