How Poisonous Is Oleander and Why Is Oleander Considered the Most Poisonous Plant In the World?

Oleander is extremely toxic, one of the most toxic plants on anyone’s list.

Even a few oleander leaves falling into a small ornamental pool could poison a dog who lapped water from the pool.

All parts of the oleander plant are considered toxic, with the seeds usually the most toxic, the leaves a little less and the flowers least, but still dangerous.

Even the stems are dangerous, and there are anecdotal reports of children poisoned by hot dogs roasted over a fire of the stems. Adults have been poisoned by consuming one leaf.

The widely used ornamental bush comes in two species, Neriurn oleander; the common pink oleander planted in California in the space dividing interstate highways, and the yellow oleander, Thevetia peruviana.

Both contain cardioactive glycosides, which are similar in effect to digitalis but much more toxic.

They can be quickly fatal.

Besides disrupting the heart function, they cause gastrointestinal symptoms like vomiting and diarrhea.

Extreme care should be taken with oleander plants and trimmings around people or animals.

Well-fed animals will not usually seek out oleander leaves, but some may accept them despite their bitter taste and consume enough to be harmed.

Those most at risk would be naive animals new to an area, or perhaps a horse who is attracted to trimmings thrown over the pasture fence.