Named after their superficial resemblance to olive trees, Oleander (Nerium oleander) is an attractive shrub or small tree that thrives in a Mediterranean climate. Originally hailing from North Africa and West Asia, property owners can now purchase oleanders in any of more than 400 different forms.
Size and Shape
Oleanders most commonly grow as large, bushy shrubs, but some specimens develop a tree-like size and shape. Most oleanders are only a few feet tall, but the largest examples may reach 20 feet in height. When large, oleanders tend to exhibit an umbrella-like growth habit. Their stems grow in a relatively narrow clump, but the tops of the branches spread out and cascade toward the ground.
Flowers and Foliage
Oleander leaves are dark green and arranged in pairs (although they occasionally feature a whorled leaf arrangement). An evergreen plant, oleander remains quite attractive throughout the year.
Nevertheless, people do not typically fall in love with oleanders because of their dark green leaves – the flowers are the oleanders’ claim to fame. Sweet-scented and abundant, oleander flowers are as beautiful as they are plentiful; they often bloom throughout the entirety of the warm season. Most oleanders have white or pink flowers, but some cultivars yield flowers ranging from yellow to red.
Unlike many other flowers that depend on the help of insects for pollination, oleanders do not appear to provide any benefit to the insects that visit them. Instead, they appear to use deceptive practices to trick bees into visiting the flowers, even though they produce no nectar on which the bees can feed.
The downy seeds are released from long, thin pods; they take to the air and drift far away when strong winds blow.
While they do not appear to be toxic to many rodents or birds, oleanders are toxic to humans and some other animals. The toxins produced by the plant may cause gastrointestinal upset, heart rhythm problems and even nervous system disturbances – in some cases consumption has resulted in death. However, many tales of oleander poisoning are little more than myths. While you should certainly avoid consuming any part of the plant (all tissues potentially bear the toxic components), human deaths from consuming the plant are relatively rare.
Some people report that contact with the sap of oleanders can cause a skin rash, so caution is advised when contacting the plants. Many insects that feed upon the leaves sequester the ingested toxins and use them as a defense mechanism. Because they are toxic, oleander trees and shrubs typically receive little damage from deer and rabbits.
Geography for Growing
Oleanders grow best in USDA Hardiness zones 8 through 10, but many people have successfully grown them outside of this range. Tough plants, oleanders can handle a wide array of challenges, including high temperatures, periodic drought, periodic flooding, compacted soils, salt spray and high pH levels. However, they are very sensitive to temperatures below about 20 degrees Fahrenheit. When exposed to such chilly temperatures, they almost always suffer damage.
However, if protected from low temperatures, oleanders can thrive just about anywhere. Many people grow them as indoor, potted plants and move them outside during the summer. Alternatively, they can be grown inside the climate-controlled confines of a greenhouse.