Valued worldwide for its ornamental properties, the oleander (Nerium oleander) grows as a distinctive shrub or small tree, with characteristically bright, showy flowers.
It is a perennial, evergreen species with erect stems and branches, and leathery dark or grey-green leaves. The leaves grow in groups of three and are generally long and narrow, with prominent veins running up the centre to the sharply pointed tips.
The oleander produces showy, often fragrant, tubular or funnel-shaped flowers which are arranged in clusters at the ends of stems. Each flower has five petals, and a base fringed with long petal-like projections. The flowers are typically red, pink or white in the wild. However, over 400 variants of the oleander have been cultivated to display a huge variety of flower colour, including varying shades of deep to pale creams, pinks, lilacs, purples, yellows, oranges and copper. The fruit is a long, narrow, bean-like capsule which splits along one side to release many seeds. Each individual seed has a plume of reddish-brown hairs, called a pappus, at one end
Nerium oleander is considered to be a very drought resistant plant, it prefers to live in a very moist habitat because in its early stages of life there is a greater need for water then in the adult stages. Oleander engages in sexual reproduction, however it can self pollinate, but this of course is not ideal because genetic diversity is very important in order to survive as a species.
When Nerium oleander is engaging in sexual reproduction it goes through the process of gametic meiosis. At the beginning of this cycle there is a multicellular diploid sporophyte that produces haploid spores via meiosis. From these spores, multicellular, haploid gametophytes, via mitosis, arise. These then produce haploid gametes, often referred to as egg and sperm, via mitosis. These then fertilize and produce a diploid zygote. This zygote, often referred to as a seed, then goes through mitosis to produce another multicellular, diploid sporophyte, starting the cycle all over.
Nerium oleander, like all flowering plants, goes through double fertilization. This process starts when the pollen grain lands on the stigma of a plant. It then creates a pollen tube that goes down through the style to the ovary of the plant. Once it has reached the ovary two sperm are released. One fuses with the egg to create the diploid zygote. The other fuses with the multiple nuclei to create the endosperm. This endosperm is the nutrient rich part of the seed that the early zygote uses to germinate and grow before it photosynthesizes for itself.
Oleander has historically been considered a poisonous plant because some of its compounds may exhibit toxicity, especially to animals, when consumed in large amounts. Among these compounds are oleandrin and oleandrigenin, known as cardiac glycosides, which are known to have a narrow therapeutic index and can be toxic when ingested. Toxicity studies of animals administered oleander extract concluded that rodents and birds were observed to be relatively insensitive to oleander cardiac glycosides. Other mammals, however, such as dogs and humans, are relatively sensitive to the effects of cardiac glycosides and the clinical manifestations of "glycoside intoxication". Oleander is a common cause of poisoning and death in tropical and subtropical countries, with 170 cases seen at a single hospital in Sri Lanka. However, prognosis is good if the patient can reach a hospital in time; several common drugs can be used to stabilize the patient and counteract the glycosides. In reviewing oleander toxicity cases seen in-hospital concluded that, except for children who might be at greater risk, "the human mortality associated with oleander ingestion is generally very low, even in cases of moderate intentional consumption (suicide attempts)".