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Oleander (Nerium oleander), is a 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), Araliya (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 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.
Additional recommended knowledge
Cultivation and uses
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 (Huxley et al. 1992). It can also be grown in cooler climates in greenhouses, conservatories, or as indoor plants that summer outside. Oleander flowers are showy and fragrant and are grown for these reasons. Over 400 cultivars have been named, with several additional flower colours not found in wild plants having been selected, including red, purple and orange; white and a variety of pinks are the most common. Many cultivars also have double flowers.
Oleander is one of the most poisonous plants and contains numerous toxic compounds, many of which can be deadly to people, especially young children. The toxicity of Oleander is considered extremely high and it has been reported that in some cases only a small amount had lethal or near lethal effects (Goetz 1998). The most significant of these toxins are oleandrin and neriine, which are cardiac glycosides (Goetz 1998). "Cardiac glycocides are naturally occurring" plant or animal compounds "whose actions include both beneficial and toxic effects on the heart" (Desai 2000). They are present in all parts of the plant, but are most concentrated in the sap. It is thought that Oleander may contain many other unknown or un-researched compounds that may have dangerous effects (Inchem 2005). Oleander bark contains rosagenin which is known for its strychnine-like effects. The entire plant including the milky white sap is toxic and any part can cause an adverse reaction. Oleander is also known to hold its toxicity even after drying. It is thought that a handful or 10-20 leaves consumed by an adult can cause an adverse reaction, and a single leaf could be lethal to an infant or child. According to the Toxic Exposure Surveillance System (TESS) in 2002 there were 847 known human poisonings in the United States related to Oleander (Watson 2003). There are innumerable reported suicidal cases of consuming mashed oleander seeds in South India. In animals, around 0.5 mg per kilogram of body weight is lethal to many animals, and various other doses will affect other animals (Inchem 2005). Most animals can suffer a reaction or death from this plant.
Effects of poisoning
Reactions to this plant are as follows. Ingestion can cause both gastrointestinal and cardiac effects. The gastrointestinal effects can consist of nausea and vomiting, excess salivation, abdominal pain, diarrhea that may or may not contain blood, and especially in horses, colic (Inchem 2005). Cardiac reactions consist of irregular heart rate, sometimes characterized by a racing heart at first that then slows to below normal further along in the reaction. The heart may also beat erratically with no sign of a specific rhythm. Extremities may become pale and cold due to poor or irregular circulation (Goetz 1998). Reactions to poisonings from this plant can also affect the central nervous system. These symptoms can include drowsiness, tremors or shaking of the muscles, seizures, collapse, and even coma that can lead to death (Goetz 1998). Oleander sap can cause skin irritations, severe eye inflammation and irritation, and allergy reactions characterized by dermatitis (Goetz 1998).
Medical treatment required
Poisoning and reactions to Oleander plants are evident quickly, requiring immediate medical care in suspected or known poisonings of both humans and animals (Goetz 1998). Induced vomiting and gastric lavage are protective measures to reduce absorption of the toxic compounds. Charcoal may also be administered to help absorb any remaining toxins (Inchem 2005). Further medical attention may be required and will depend on the severity of the poisoning and symptoms.
Drying of plant materials does not eliminate the toxins. It is also hazardous for animals such as sheep, horses, cattle, and other grazing animals, with as little as 100 g being enough to kill an adult horse (Knight 1999). Plant clippings are especially dangerous to horses, as they are sweet. Symptoms of a poisoned horse include severe diarrhea and abnormal heartbeat. There are a wide range of toxins and secondary compounds within Oleander, and care should be taken around this plant due to its toxic nature. Different names for Oleander are used around the world in different locations (see top of page); so when encountering a plant with this appearance, regardless of the name used for it, exercise great care and caution to avoid ingestion of any part of the plant, including its sap and dried leaves or twigs. Do not use the dried or fresh branches for spearing food, in preparing a cooking fire, or as a food skewer. Many of the Oleander relatives, such as the Desert Rose (Adenium obesum) found in East Africa, have similar leaves and flowers and are equally toxic.
While the reasons are unknown, some visibly healthy oleander shrubs that have become sick or otherwise diseased may generate a type of oil from the trunk and shallow roots. Depending upon the size of the shrub, the oil quantity can vary greatly and has the capability to saturate the soil in its vicinity as the shrub's sickness progresses. This is possibly an explanation for the plant's name of "Olea", whose Latin translation is "oil". The oil is light-brown colored and possesses a rancid scent. The toxicity of the oil is unknown, because the neuro-toxic chemicals in the rest of the tree come from the leave's vein-system and not from the actual pulp surrounding these veins. There is even a species of large, green caterpillar who feeds specifically on oleanders and survives by eating only the pulp surrounding the leaf-veins, avoiding the fibers.
Potential medical use
Pliny the Elder in his Naturalis Historia written circa AD 77 claimed that despite its toxicity it was an effective snakebite cure: "...if taken in wine with rue..." .
An extract "Anvirzel" has been developed completed Phase I testing in 2000 to judge its effectiveness as a cancer treatment. Despite such trial not yet showing benefits, this and a range of other Oleander-based treatments are being promoted on the Internet and in some alternative medicine circles, drawing warning letter from the FDA in the US.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Oleander". A list of authors is available in Wikipedia.|