Nerium oleander

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Nerium oleander

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Family Apocynaceae
Genus Nerium
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About

File:Nerium oleander wild2.jpg
Oleander shrub, Morocco

Nerium oleander ()<ref>Sunset Western Garden Book, 1995:606–607</ref> is an evergreen shrub or small tree in the dogbane family Apocynaceae, toxic in all its parts. It is the only species currently classified in the genus Nerium. It is most commonly known as oleander, from its superficial resemblance to the unrelated olive Olea<ref>Cf. oleaster.</ref>, but has many other names.<ref name=Names>Other names include Adelfa, Alheli Extranjero, Baladre, Espirradeira, Flor de São Jose, Cevadilha (Portuguese), Laurel de jardín, Laurel rosa, Laurier rose, Flourier rose, Olean, Aiwa, Rosa Francesca, Rosa Laurel, and Rose-bay (Inchem 2005), закум [zakum] (Bulgarian), leander (Hungarian), leandru (Romanian), zakum, zakkum, zakhum (Turkish), zaqqum (Arabic); harduf (Hebrew: הרדוף); Kaneru (Sinhalese);arali (Tamil and Malayalam - South Indian languages); kanagillu (Kannada - South Indian language); kaner (in Hindi, and, also, in Punjabi-the language from North Indian state of Punjab); and in Chinese it is known as jia zhu tao ().</ref> It is so widely cultivated that no precise region of origin, perhaps in southwest Asia, has been identified. The ancient city of Volubilis in Morocco took its name from the old Latin name for the flower. Oleander is one of the most poisonous of commonly grown garden plants, and can be very toxic if ingested in sufficient quantity.

Description

Oleander grows to tall, with erect stems that splay outward as they mature; first-year stems have a glaucous bloom, while mature stems have a grayish bark. The leaves are in pairs or whorls of three, thick and leathery, dark-green, narrow lanceolate, long and broad, and with an entire margin. The flowers grow in clusters at the end of each branch; they are white, pink to red,<ref>The "Yellow Oleander" is Thevetia peruviana.</ref> diameter, with a deeply 5-lobed fringed corolla round the central corolla tube. They are often, but not always, sweet-scented.<ref>In the past, scented plants were sometimes treated as the distinct species N. odorum, but the character is not constant and it is no longer regarded as a separate taxon.</ref> The fruit is a long narrow capsule long, which splits open at maturity to release numerous downy seeds.

Habitat and range

N. oleander is native or naturalized to a broad area from Mauritania, Morocco, and Portugal eastward through the Mediterranean region and the Sahara (where it is only found sporadically), to the Arabian peninsula, southern Asia, and as far East as Yunnan in southern parts of China.<ref name=Europa>Pankhurst, R. (editor). Nerium oleander L. Flora Europaea. Royal Botanic Garden Edinburgh. Retrieved on 2009-07-27.</ref><ref name=China>Bingtao Li, Antony J. M. Leeuwenberg, and D. J. Middleton. "Nerium oleander L.", Flora of China. Harvard University. Retrieved on 2009-07-27.</ref><ref name=Inchem>INCHEM (2005). Nerium oleander L. (PIM 366). International Programme on Chemical Safety: INCHEM. Retrieved on 2009-07-27</ref><ref name=Huxley>Huxley, A.; Griffiths, M.; Levy, M. (eds.) (1992). The New RHS Dictionary of Gardening. Macmillan. ISBN 0-333-47494-5.</ref> It typically occurs around dry stream beds. Nerium oleander is planted in many subtopical and tropical areas of the world. In the East Coast of the US, it can be planted as far north as the Outer Banks, North Carolina, while in Southern California it is naturalized as a median strip planting.

Garden history

Theophrastus in his Enquiries into Plants of ca. 300 BCE described among plants that affect the mind a shrub he called onotheras, which modern editors render oleander; "the root of onotheras [oleander] administered in wine," he alleges, "makes the temper gentler and more cheerful."

"The plant has a leaf like that of the almond, but smaller, and the flower is red like a rose. The plant itself (which loves hilly country) forms a large bush; the root is red and large, and, if this is dried, it gives off a fragrance like wine."

In another mention, of "wild bay" (Daphne agria), Theophrastus appears to intend the same shrub.<ref>{Theophrastus), Inquiry into Plants, A. F. Hort, tr. (Loeb Classical Library, I.9.3; IX.19.1.</ref>

Uses

File:Purity.jpg
Bud of a white-flowered cultivar

Ornamental

Oleander grows well in warm subtropical regions, where it is extensively used as an ornamental plant in landscapes, in parks, and along roadsides. It is drought-tolerant and will tolerate occasional light frost down to .<ref name=Huxley/> It is commonly used in landscaping freeway medians in California and other mild-winter states in the Continental United States because it is upright in habit and easily maintained. Its toxicity renders it deer-resistant. It is tolerant of poor soils and drought. Oleander can also be grown in cooler climates in greenhouses and conservatories, or as indoor plants that can be kept outside in the summer. 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, pink, and orange; white and a variety of pinks are the most common. Many cultivars also have double flowers. Young plants grow best in spaces where they do not have to compete with other plants for nutrients.

Toxicity

Oleander is one of the most poisonous plants in the world and contains numerous toxic compounds, many of which are deadly to people, especially young children. (Despite this fact, it is often grown in school yards.<ref>[1] Encyclopedia of Stanford Trees, Shrubs, and Vines: Nerium oleander.</ref>)

Pliny the Elder in his Naturalis Historia written circa AD 77 writes of this "rose-tree" (rhododendron<ref>The modern genus name Rhododendron applies to woody plants unknown to Pliny.</ref>)


Ancient advice to counter poison with poison, like this, may often have deadly results, as Pliny's antidote would have.

Despite a lack of any proven benefits,<ref>Phase I Study of AnvirzelTM in Patients with Advanced Solid Tumors. American Society of Clinical Oncology. Retrieved on 2009-07-27.</ref> a range of oleander-based treatments are being promoted on the Internet and in some alternative medicine circles, drawing a warning letter from the U.S. Food and Drug Administration (FDA).<ref>Food and Drug Administration: Anvirzel Letter, dated March 7, 2000. Retrieved on 2009-07-27.</ref> In addition, a Texas-based biotechnology company is researching oleander as a potential treatment for skin cancers, as well as an anti-viral treatment.<ref>http://www.nerium.com/index-2.html</ref>

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.<ref name=Goetz>Goetz, Rebecca. J. (1998). "Oleander". Indiana Plants Poisonous to Livestock and Pets. Cooperative Extension Service, Purdue University. Retrieved on 2009-07-27.</ref> The most significant of these toxins are oleandrin and neriine, which are cardiac glycosides.<ref name=Goetz/> They are present in all parts of the plant, but are most concentrated in the sap, which can block out receptors. High-risk circumstances of exposure include children playing with the ornamental shrub, as well as adults or children tasting, chewing, and ingesting portions of the plant [2], and inappropriate medicinal use of plant infusion.<ref name="Inchem"/> Oleander bark contains rosagenin, which is known for its strychnine-like effects. The entire plant, including the nectar,<ref name="NLM">"Oleander poisoning". MedlinePlus. U.S. National Library of Medicine. http://www.nlm.nih.gov/medlineplus/ency/article/002884.htm. Retrieved 2010-06-26. </ref> 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 exposures to oleander reported to poison centers in the United States.<ref name=Watson>Watson, William A., et al. 2003. 2002 Annual Report of the American Association of Poison Control Centers Toxic Exposure Surveillance System. American Journal of Emergency Medicine 21 (5): 353-421.</ref> There are innumerable reported suicidal cases of consuming mashed oleander seeds in southern India. Around 0.23 mg per pound of body weight is lethal to many animals, and various other doses will affect other animals. Most animals can suffer a reaction or death from this plant.<ref name=Inchem/>

Effects of poisoning

File:Oleandrin.png
Oleandrin, one of the toxins present in Oleander

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.<ref name=Inchem/> 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. 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. Oleander sap can cause skin irritations, severe eye inflammation and irritation, and allergy reactions characterized by dermatitis.<ref name=Goetz/>

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.<ref name=Goetz/> 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.<ref name=Inchem/> Further medical attention may be required and will depend on the severity of the poisoning and symptoms. Temporary cardiac pacing will be required in many cases (usually for a few days) till the toxin is excreted.

Digoxin Immune Fab is the best way to cure an oleander poisoning if inducing vomiting has no or minimal success, although it is usually used only for life-threatening conditions due to side-effects.

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.<ref name=Knight>Knight, A. P. (1999). "Guide to Poisonous Plants: Oleander". Colorado State University. Retrieved on 2009-07-27.</ref> Plant clippings are especially dangerous to horses, as they are sweet. In July 2009, several horses were poisoned in this manner from the leaves of the plant.<ref>Trevino, Monica. 2009.Dozens of horses poisoned at California farm. CNN: Crime. Retrieved on 2009-08-03</ref> Symptoms of a poisoned horse include severe diarrhea and abnormal heartbeat. There is 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, so, when encountering a plant with this appearance, regardless of the name used for it, one should exercise great care and caution to avoid ingestion of any part of the plant, including its sap and dried leaves or twigs. The dried or fresh branches should not be used for spearing food, for 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.

Trunk oil

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 of a light-brown color 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 leaves' vein-system and not from the pulp surrounding these veins.

Ecology

Some invertebrates are known to be unaffected by oleander toxins, and feed on the plants. Caterpillars of the Oleander or Polka-Dot Wasp Moth (Syntomeida epilais) feed specifically on oleanders and survive by eating only the pulp surrounding the leaf-veins, avoiding the fibers. Larvae of the Common Crow Butterfly (Euploea core) also feed on oleanders. The Common Crow larvae retain or modify toxins, making them unpalatable to would-be predators such as birds, but not to other invertebrates such as spiders and wasps.

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