OLEANDER: CHARACTERISTICS, HABITAT, CULTIVATION, USES - BIOLOGY - 2025

The oleander (Nerium oleander) is a highly toxic perennial shrubby species belonging to the family of the Gentianales Apocynaceae order. Known as baladre, flower laurel, Roman laurel, laurel rose or trinitaria, it is a native species of the Mediterranean basin.

It is a plant widely used as an ornamental due to its showy, brightly colored flowers that grow terminally on its branches. As a commercial crop, several varieties of different colors have been developed, which makes them very popular in warm and temperate environments.

Oleander (Nerium oleander). Source: pixabay.com

The plant is an evergreen shrub 3-6 m tall, with green and flaccid stems, branching from the base. The lanceolate, elongated, whole and leathery gray-green leaves are grouped in whorls of three leaves.

Summer flowering occurs abundantly during spring and summer with flowers of various colors, mainly pink and white. The fruit is made up of long thin follicles that open to release numerous hairy seeds.

- Species: Nerium oleander L.

Etymology

- Nerium comes from the Greek word "Nerion" derived from the Latin "Nerium", referring to "Nereus" the God of the sea and father of the Nereids.

- Oleander is an adjective derived from the Latin «Olea», due to the similarity of its leaves to the olive tree, and «dendron» from the tree.

- The common name Adelfa comes from the Greek "Dafne" due to its similarity to the laurel, derived in turn from the Arabic "diflá".

Oleander fruits. Source: Pablo Alberto Salguero Quiles

Photochemistry

Oleander leaves contain cardiac steroids or cardenolides, such as deacetyloleandrin, oleandrin or oleandrigenin, whose genins are gitoxigenin and digitoxigenin. As well as pregnanes or 21-carbon steroids and pregnane glucans such as 12β-hydroxy-16α-metfioxy-pregna-4,6 diene-3,20-dione.

Flowers are the main source of photochemicals, such as flavonoids and phenolic compounds, oleandrin, oleanolic acid, and β-sitosterol. Compounds of high pharmacological value widely used in the treatment of heart failure and against various types of cancer.

Habitat and distribution

Nerium oleander is a species native to the Mediterranean basin to the southeast region of China, bordering Vietnam. At present it has been widely introduced in temperate climate regions, being frequently used in parks, gardens, as hedges, flower beds or separators.

Oleander is a plant that adapts to dry weather conditions that tolerates low temperatures, but only occasional frosts. It is a shrub resistant to strong winds, high temperatures, seasonal drought and tolerates slightly arid soils.

This species is distributed in America, from the United States, where it is considered invasive in some urban environments, to Panama, Venezuela, Colombia, Uruguay and Argentina. Likewise, it has adapted to arid and dry temperate conditions in southern European countries, Asia and Australia.

Oleander seeds. Source: Júlio Reis

Cultivation and care

Nursery culture

The natural propagation of oleander is done through seeds, but commercially the propagation is done by means of cuttings. Cuttings are selected from healthy and vigorous mother plants, grown in the wild or under greenhouse conditions.

The production process at the nursery level lasts one year. Indeed, the selection of the cuttings, 15-20 cm long and with 2-3 knots, is done at the end of winter.

The cuttings are sown in rooting trays on a substrate of blond peat and perlite, pH 6.5 and lightly fertilized. An average temperature of 25-30º C, continuous irrigation by aspersion and polisombra of 65%, allow to reach the rooting at 30 days.

Transplantation is carried out at 30-45 in pots or polyethylene bags with a loose and fertile substrate. It is recommended to sow 2-3 rooted cuttings per pot in order to obtain a plant with dense foliage.

60 days after transplanting, it is advisable to perform apical pruning so that the plant forms a clump and generates new stems. In addition, this practice allows to stimulate the sprouting of a greater number of flower buds, thus obtaining a more ornamentally productive plant.

Crop management requires periodic fertigation together with dwarfing products that compact the development of the plant. Applications are made at weekly intervals, depending on each variety grown.

During the winter the vegetative rest of the plant begins, thus stimulating the proliferation of flower buds. In fact, flowering begins in early spring, during the months of April-May of next year. This being the opportune moment to start the sale.

Oleander seedling. Source: Bff

Handling and care

Oleanders are plants resistant to adverse conditions that require minimal care for their optimal development. However, it is convenient to provide the right conditions for the plant to express its maximum potential during the flowering process.

Floors

As an ornamental it adapts to various types of terrain, preferring loose, deep, fertile and well-drained soils. Grown in pots, it requires large and deep containers with a nutritious substrate to express its greater productive development.

Lighting and temperature

Oleander is a plant that requires good lighting, it is recommended to sow in open spaces, in full sun exposure. Furthermore, it adapts to a wide temperature range, being susceptible to frosts below 10º C, suffering damage to flower buds.

Irrigation

It is a plant that requires moderate but constant watering to prevent the soil from drying out for long periods. The main objective of irrigation is to facilitate the absorption of nutrients applied by fertilization to promote greater vegetative development.

Fertilization

It is recommended the application of organic fertilizer or granulated fertilization diluted in the irrigation water or dispersed broadcast around the plant. Frequent fertilization with a product with a balanced content of NPK and microelements is appropriate to ensure intense flowering.

Pruning

Pruning is performed at the end of flowering in order to stimulate the formation of new shoots and give the plant vigor. Indeed, these shoots during the winter will have time to create a greater number of flower buds.

Oleander adult plant. Source: Alpha Centauri

Plagues and diseases

The main pests that cause commercial damage to oleander are spider mites, mealybugs and aphids. Other pests of lesser incidence and occasionally are snails, slugs and some type of beetle or lepidopteran caterpillar.

Red spider mites (Tetranychus urticae) usually occur in dry and warm seasons, being controlled with specific applications of acaricides. The highest incidence of aphids (Aphis sp.) Is on young shoots; they are virus transmitting insects, their control is carried out with systemic insecticides.

Mealybugs (Planococcus sp., Dactylopius sp.) Are very difficult insects to control due to their protective shell. They are usually located in the stems or in the veins of the leaves, their control is carried out with systemic insecticides and mineral oils.

Of the diseases, the one caused by the bacterium Pseudomonas syringae is common in wild-grown plants. Transmission is carried out through contaminated pruning tools, the main symptoms being galls and deformations at the stem level.

Aphis attack on oleander shoots. Source: Юкатан

Medical uses

Oleander contains various metabolites that provide it with medicinal properties, mainly related to the cardiovascular system and the heart. These elements include oleandrin, a cardiac glycoside that is used to treat heart failure.

However, this element is highly toxic, so its traditional use can be harmful if consumed without medical supervision. Preliminary laboratory tests have made it possible to determine its effectiveness, but studies in patients are still required to support its effectiveness.

On the other hand, due to the way oleandrin works in the body, it follows that it can be used to fight cancer. In fact, oleandrin slows cell growth, being useful in treating cancer in its early stages.

Toxicity

Oleander is a very toxic plant, due to the presence of the cardiac glycosides digitoxigenin, folinerin and oleandrin. The whole plant contains these compounds, being in the root and the seeds where the highest concentrations occur.

Because it is a very striking ornamental plant, people tend to get intoxicated when chewing its leaves or flowers without realizing the danger. Signs of intoxication are general malaise, hypotension, dizziness, confusion, nausea, vomiting, and oral-gastrointestinal irritation with abdominal pain.

Nerium oleander. Source: Bff

Similarly, combustion of oleander foliage, stems, and branches produces poisonous gases that can affect people. It affects the digestive system and the heart, and to a lesser extent the nervous system and motor skills.

References

1. Oleander (Nerium oleander) (2010) Ministry of Health of the Region of Murcia. Recovered in: murciasalud.es
2. Céspedes Valcarcel, A., Corral Salvadó, A., Díaz Olivera, C., & Morales Fundora, Y. (1999). Effect of nerium oleander l: On isolated guinea pig heart model. Cuban Journal of Medicinal Plants, 4 (2), 74-78.
3. Farooqui, S. & Tyagi, T. (2018) Nerium oleander: It's Application In Basic And Applied Science: A Review. International Journal of Pharmacy and Pharmaceutical Sciences. Vol. 10, Issue 3. ISSN: 0975-1491.
4. Faustino, GP, Gerardo, HM, Reynaldo, LF, & Julián, CR (2008). Production of oleander nerium oleander in Morelos. Technical Brochure No. 32. National Institute of Agricultural and Livestock Forestry Research. South Pacific Regional Research Center "Zacatepec" Experimental Field. Mexico.
5. Martínez Castro, B., Ferrando Piqueres, R., & Milara Payà, J. (2007). Nerium oleander poisoning (baladre): two clinical cases. Hospital Pharmacy, 31 (2), 134-135.
6. Nerium oleander (2019) Outdoor plants. Tree and Plant Species. Recovered at: elarbol.org
7. Nerium oleander (2019) Plants and Flowers. Outdoor Plants. Recovered in: floresyplantas.net
8. Nerium oleander (2019). Wikipedia, The Free Encyclopedia. Recovered at: es.wikipedia.org
9. Porcuna, JL (2013) Plants Technical Sheet. Plant Health Service. Valencia. Ae No. 12.