Adelfa flowers (Nerium Oleander)

Nerium oleander is a shrub or small tree in the dogbane family Apocynaceae, toxic in all its parts. It is theconly species currently classified in the genus Nerium.
It is most commonly known as nerium or oleander, from its superficial resemblance to the unrelated olive Olea.
It is so widely cultivated that no precise region of origin has been identified, though southwest Asia has been suggested.
The ancient city of Volubilis in Morocco may have taken its name from the Berber name oualiltfor the flower.
Oleander is one of the most poisonous commonly grown garden plants.

Oleander grows to 2–6 m (6.6–19.7 ft) 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, 5–21 cm (2.0–8.3 in) long and 1–3.5 cm (0.39–1.38 in) broad, and with an entire margin filled with minute reticulate venation web typical to Eudicots.
Leaves are light green and very glossy when young, before maturing to a dull dark green/greenish gray.
The flowers grow in clusters at the end of each branch; they are white, pink to red, 2.5–5 cm (0.98–1.97 in) diameter, with a deeply 5-lobed fringed corolla round the central corolla tube. They are often, but not always, sweet-scented.
The fruit is a long narrow pair of follicles 5–23 cm (2.0–9.1 in) long, which splits open at maturity to release numerous downy seeds.

N. oleander is either 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.

It typically occurs around stream beds in river valleys, where it can alternatively tolerate long seasons of drought and inundation from winter rains. 
Nerium oleander is planted in many subtropical and tropical areas of the world. On the East Coast of the US, it grows as far north as Virginia Beach, Virginia, while in California and Texas miles of oleander shrubs are planted on median strips.
There are estimated to be 25 million Oleanders planted along highways and roadsides throughout the State of California. Because of its durability, Oleander was planted prolifically on Galveston Island in Texas after the disastrous Hurricane of 1900. They are so prolific that Galveston is known as the 'Oleander City'; an annual Oleander festival is hosted every spring.

Some invertebrates are known to be unaffected by oleander toxins, and feed on the plants. Caterpillars of the 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, and they retain or modify toxins, making them unpalatable to would-be predators such as birds, but not to other invertebrates such as spiders and wasps.

The flowers require insect visits to set seed, and seem to be pollinated through a deception mechanism. The showy corolla acts as a potent advertisement to attract pollinators from a distance, but the flowers are nectarless and offer no reward to their visitors. They therefore receive very few visits, as typical of many rewardless flower species.
Fears of honey contamination with toxic oleander nectar are therefore unsubstantiated.

Drugs derived from N. oleander have been investigated as a treatment for cancer, unsuccessfully.
According to the American Cancer Society, the trials conducted so far have produced no evidence of benefit, while they did cause adverse side effects.
A company called Nerium International markets anti-aging creams with extract from the Oleander as the active ingredient; its efficacy has not been scientifically verified.

Oleander has historically been considered a poisonous plant because some of its compounds may exhibit toxicity, especially to animals, when consumed in large amounts. Among these compounds are oleandrin and oleandrigenin, known as cardiac glycosides, which are known to have a narrow therapeutic index and can be toxic when ingested.

Toxicity studies of animals administered oleander extract concluded that rodents and birds were observed to be relatively insensitive to oleander cardiac glycosides.
Other mammals, however, such as dogs and humans, are relatively sensitive to the effects of cardiac glycosides and the clinical manifestations of "glycoside intoxication".

However, despite the common "poisonous" designation of this plant, very few toxic events in humans have been reported. According to the Toxic Exposure Surveillance System, in 2002, 847 human exposures to oleander were reported to poison centers in the United States. Despite this exposure level, from 1985 through 2005, only three deaths were reported. One cited death was apparently due to the ingestion of oleander leaves by a diabetic man. His blood indicated a total blood concentration of cardiac glycosides of about 20 μg/l, which is well above the reported fatal level. Another study reported on the death of a woman who self-administered "an undefined oleander extract" both orally and rectally and her oleandrin tissue levels were 10 to 39 μg/g, which were in the high range of reported levels at autopsy. In 2000, the death of two toddlers in El Segundo was attributed to eating oleander.

In contrast to consumption of these undefined oleander-derived materials, no toxicity or deaths were reported from topical administration or contact with N. oleander or specific products derived from them. In reviewing oleander toxicity, Lanford and Boor concluded that, except for children who might be at greater risk, "the human mortality associated with oleander ingestion is generally very low, even in cases of moderate intentional consumption (suicide attempts)".

Toxicity studies conducted in dogs and rodents administered oleander extracts by intramuscular injection indicated that, on an equivalent weight basis, doses of an oleander extract with glycosides 10 times those likely to be administered therapeutically to humans are still safe and without any "severe toxicity observed".

Ingestion of this plant can affect the gastrointestinal system, the heart, and the central nervous system. The gastrointestinal effects can consist of nausea and vomiting, excess salivation, abdominal pain, diarrhea that may contain blood, and especially inhorses, colic. 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. Extremities may become pale and cold due to poor or irregular circulation. The effect on the central nervous system may show itself in symptoms such as 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 allergic reactions characterized by dermatitis.