The wicked beauty of Oleander

Oleander (la adelfa) is one of the most beautiful but deadly flowers in the world. Oleander is very decorative and drought tolerant, and stays green year-round. No wonder it is used as an ornamental plant in Mediterranean gardens, parks, promenades and any public place you can think of. It's not really a landmark, but landmark-ish; you are bound to run into at least one of the Oleander shrubs when you are in Seville. Here in Andalusia, Oleander is common for landscaping, though intensely poisonous, as it is a fast-growing evergreen. Its flowers can be vibrant pink, yellow, red or white and it is attractive when planted as a median barrier on the central reservations of Andalusian motorways to shield drivers from the effects of on-coming headlights, that is to say, to avoid dazzle between vehicles driving in opposite directions.

Oleander shrubs on the A49 motorway towards Huelva. Photo by Sevilla +VERDE

All these thousands and thousands of flowering shrubs used for motorways have many benefits: they are pleasing on eye, and they are, at the same time, absorbing carbon dioxide, filtering out particulate pollutants, such as atmospheric dust, increasing oxygen levels and humidity, and decreasing air temperature.

Pruning the Oleanders that delimit the central reserves in San Jerónimo neighbourhood in Seville. Photo by ABCdesevilla.es

Speaking of its lethality, cardiac glycosides found in the flowering shrub Oleander are said to be fatally toxic even in small doses, even if only one leaf is ingested. Glycosides can have severe toxic effects on the body, including the heart and other vital organs. Ingesting any type of extracts derived from Oleander leaves or seeds or the raw plant itself can cause Oleander poisoning. I've read a few sources stating that Oleander is not even a good source for bee forage in that the resulting honey is toxic. You can become poisoned just by breathing in it's smoke or by eating Oleander honey, so they say.

Close-up of an Oleander flower. Photo by Montse

The chances are that this is true. Henry Vollam Morton, a British travel writer, insists in his 1964 book about his adventures in Italy (see the references) that there are three categories of plants that are associated with toxic honey:

• plants whose nectar or pollen kills bees before they can transform it into honey (e.g. Locoweed, Veratrum californicum, Vernonia spp.);
• plants whose nectar is harmless to bees but when turned into honey becomes toxic to humans (e.g. Oleander, Thorn apple, Angel's trumpet, Mountain laurel, False jasmine, Euphorbia marginata, Serjania lethalis); and
• known poisonous plants that are harmless to bees and yield edible and often exquisite honey (e.g., Rhustoxicodendron, Metopium toxiferum, Jatropha curcas, Baccharis halimifolia, Ricinus communis).

But then, I tend to agree with some of the Gotmead Forum comments on this issue that the poisonous indigestible sap of Oleander can be irritating to the eyes and skin, but if the nectar was poisonous, the bees would die from consuming it. So, if the bees can eat it and make honey from it, it is not poisonous.