Without question oleander, frequently used as an ornamental shrub, is a beautiful plane. It grows as a shrub or small tree to twenty feet call, although many gardeners trim it back to a more manageable size. The leaves are evergreen narrowly lance-shaped, three to ten inches long, with rather conspicuous veins; either two or three leaves are found at a node. The flowers, one to three inches across, are borne in clusters of five to eight, and may be purple, pink or white. Each flower consist of five petals forming a central cube, with toothed scales at the mouth of the cube.
Oleander has been known as a poisonous plant since classical times, with all the major Greek and Roman natural history writers (Dioscorides, Pliny, Galen) including descriptions of its dangerous properties. All parts of the plant, fresh or dry, are considered highly toxic to both livestock and humans; the leaves, flowers, seeds, and even nectar should be avoided at all cost. Cattle, horses, and sheep have been killed by small doses of the plant; children have been poisoned from carrying flowers in their mouths; smoke inhaled from burning plants has caused serious respiratory problems; contact with leaves or sap may
cause dermatitis; honey made from oleander nectar is bitter and toxic. And people have died simply from eating meat roasted on oleander stems!
The symptoms of oleander poisoning are none too pleasant: severe gastroenteritis with dizziness, drowsiness, increased pulse rate, vomiting and abdominal pain followed by an irregular and weakened heartbeat, breathing
difficulties, coma, and eventually, death. These symptoms commence within a few hours of contact; death, if it occurs, will take place within twenty-four hours.
Biochemists, attracted by the sheer power of its toxin, have traced the poisonous nature of oleander to a group of chemicals called cardiac glycosides. Like many other compounds produced by plants, these substances are thought to retard the depredations of would-be consumers, such as insects and mammals. They act by boosting the contractility of the heart; as a result, the heartbeat may weaken, leading to cardiac arrest.
As is frequently the case, only a small degree separates a harmful chemical action from one that may be beneficial to humans, and a number of plant-produced cardiac glycosides have proved useful to medicine. The most notable one, digitalis (obtained from foxglove), has long been used to stabilize irregular heartbeats. Unfortunately, nerioside and oleandroside--which are named after their source, Nerium oleander--have proved far too toxic to be tamed, and no positive use has been discovered for them.
So what do we do with this plant? Although not native to our state, it has carved itself a permanent home here. While the oleander is a beautiful ornamental shrub, it should only be admired from afar. Its arsenal of protective chemicals has tremendous medical potential, but, as yet, that arsenal cannot be controlled. With its strange set of qualities, the oleander deserves both our respect and our fear--especially when one is choosing skewers for a Gulf Coast weenie roast.