Oleanders are commonly used in landscaping along fences for privacy and for their beauty. Nerium oleander is a popular ornamental garden plant due to its beauty and tolerance of poor soil and drought, but unfortunately itâs very toxic to many species of animals. Oleander (Nerium oleander) is a hardy, easy-to-grow flowering plant, mainly found in the lower half of the US.Apart from making an appearance in gardens from coast to coast, in many states â including California â ⦠Unfortunately, the Oleander plant is toxic for all ⦠Dogs, cats, goats, cattle, sheep, camelids, budgerigaries, rabbits and horses are all species that have been affected by oleander. Is oleander poisonous? Oleanders are beautiful flowering plants that can grow incredibly large. Nerium oleander is a highly toxic plant from the Apocynaceae family. Oleander poisoning: The oleander is a flowering shrub or small tree which bears clusters of flowers. The plant originated from Eurasia and is often used as an ornamental plant. The plant contains chemicals (cardiac glycosides: nerioside, oleandroside; saponins) which are very toxic if ingested. Oleander poisoning: Introduction. Rule number one: Always listen to your mama. Unfortunately, oleander in the landscape is considered to be highly toxic whether the plant is fresh or dried. Poisonous Plants for Dogs and Cats: Oleander. The good news is that there have been very few reports of human death due to oleander toxicity, probably due to the plantâs vile taste, says University of Wisconsinâs BioWeb. Oleander Toxicity.