A genus of about 20-30 species of shrubs or small trees native to tropical and subtropical regions of Africa, Australia and Asia.
The species have maximum height between 2 and 10 m, with spiny branches. The leaves are waxy and oblong, 3-8 cm long. The flowers are produced throughout most of the year; they are 1-5 cm diameter, with a five-lobed white or pink corolla; some have a fragrance reminiscent of Gardenia. The fruit is a plum-shaped berry, red to dark purple-black in different species, 1.5-6 cm in length, and containing up to 16 flat brown seeds. The fruit are edible but tart, with strawberry or apple-like flavour. If eaten before fully ripe, a bitter, latex-like substance is released from the skin. Because of its abundance of sharp thorns, the plant is often used as a security hedge.
Nerium oleander, is an evergreen shrub or small tree. It is the only species currently classified in the genus Nerium. It typically occurs around dry stream beds. It grows to 2-6 m tall, with spreading to erect branches. The leaves are in pairs, 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 sweetly scented. The fruit is a long narrow capsule 5-23 cm long, which splits open at maturity to release numerous seeds.
Oleander grows well in warm subtropical regions, where it is extensively used as an ornamental plant in landscapes, parks, and along roadsides. It is drought tolerant and will tolerate occasional light frost down to -10°C. It is tolerant of a variety of poor soils and drought tolerant. It can also be grown in cooler climates in greenhouses and conservatories, or as indoor plants that can be kept outside in the summer. Over 400 cultivars have been named, with several additional flower colours not found in wild plants having been selected, including red, purple, pink and orange; Many cultivars also have double flowers.
Thevetia peruviana is a plant probably native to Mexico and Central America and a close relative to Nerium oleander. It is an evergreen tropical shrub or small tree that bears yellow or orange-yellow, trumpet like flowers and its fruit is deep red/black in color encasing a large seed that bears some resemblance to a Chinese nut. All parts of the plant are extremely poisonous, especially the seeds. Its leaves are long, lance shaped and green in colour. Leaves are covered in waxy coating to reduce water loss (typical of oleanders). Its stem is green turning silver/gray as it ages. Can be grown as shrub or tree outside in warmer climates but in frost prone areas best brought back inside for winter. Will tolerate most kinds of soil as long as they are well drained and is situated in full sun in a sheltered area. Useful as a landscaping plant in warmer climates as it does not need much maintenance.
Propagate by seed in spring (clean seed coat in a glass containing 10% bleach 90% warm water for 2-3min; after wash seed and soak in warm water for 24h). Can also propagate from cuttings in spring-early summer with hardwood cuttings.
References : Wikipedia
Here is a collection of the hybrids i grow