Oleander (Nerium oleander), is an evergreen shrub or small tree in the dogbane family Apocynaceae. It is the only species currently classified in the genus Nerium. Other names include Adelfa, Alheli Extranjero, Baladre, Espirradeira, Flor de São Jose, Laurel de jardín, Laurel rosa, Laurier rose, Flourier rose, Olean, Aiwa, Rosa Francesca, Rosa Laurel, and Rose-bay (Inchem 2005), закум [zakum] (Bulgarian), leandru (Romanian), zakum, zakkum, zakhum (Turkish), zaqqum (Arabic); Kaneru (in Sinhalese); in Chinese it is known as 夹竹桃 (jia zhu tao). The ancient city of Volubilis in North Africa took its name from the old Latin name for the flower.
It is native to a broad area from Morocco and Portugal eastward through the Mediterranean region and southern Asia to Yunnan in southern parts of China (Flora Europaea; Flora of China; Huxley et al. 1992; www.inchem.org). It typically occurs around dry stream beds. It grows to 2-6 m tall, with spreading to erect branches. The leaves are in pairs or whorls of three, thick and leathery, dark green, narrow lanceolate, 5-21 cm long and 1-3.5 cm broad, and with an entire margin. The flowers grow in clusters at the end of each branch; they are white, pink, red or yellow, 2.5-5 cm diameter, with a deeply 5-lobed corolla with a fringe round the central corolla tube. They are often, but not always, sweetly scented. The fruit is a long narrow capsule 5-23 cm long, which splits open at maturity to release numerous downy seeds.
In the past, scented plants were sometimes treated as a distinct species N. odorum, but the character is not constant and it is no longer regarded as a separate taxon.