Nerium oleander

The genus

Wu, Raven & Hong (eds.). Flora of China, vol. 16, p. 173 — Apocynaceae, Nerium Linnaeus, Science Press (Beijing) / Missouri Botanical Garden Press / eFloras.org · www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=122175 · 2026-10-10

Nerium L. (Sp. Pl. 1: 209, 1753) comprises evergreen trees or shrubs with watery sap. Leaves are in whorls of three, with the midvein prominent on the abaxial surface and numerous parallel lateral veins. Inflorescences are terminal corymbs. The corolla is funnelform, cylindric near the base, with a wide open throat and lobes overlapping to the right; the corona has five large, fringed, petal-like segments. Stamens are inserted at the apex of the corolla tube; the anthers are sagittate and pilose, carry a bristly filiform apical appendage, and are connivent and adherent to the pistil head; there is no disc. The two ovaries are distinct, with numerous ovules in each locule, and the follicles remain united until just before dehiscence. Seeds are numerous and densely pilose, with a coma at the truncate apex. Flora of China treats the genus as having one species, from Asia, Europe and North Africa.

Morphology

Flora of North America Editorial Committee (eds.). Flora of North America North of Mexico, vol. 14 — Apocynaceae, Nerium oleander Linnaeus, Flora of North America Association / eFloras.org · www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200018424 · 2026-10-10

The petiole is 2–7 mm. The leaf blade is oblong-lanceolate, 2–15(–30) × 0.5–2.5(–3.5) cm, coriaceous, with a cuneate base, revolute margins and an acuminate apex; it is pubescent abaxially and very sparsely pubescent or glabrous adaxially. Peduncles are 3–6 cm and pedicels 5–8 mm, both pubescent.

Calyx lobes are lanceolate to ovate-lanceolate, 5–7 mm. The corolla is glabrous outside; the tube is 8–12 × 2–3 mm, the throat 5–10 × 4–7 mm, and the spreading, obliquely obovate lobes 15–25 × 10–20 mm. Follicles are 8–15 × 1–1.5 cm and seeds 7–10 × 1.5–2 mm, densely pubescent. The chromosome number is 2n = 22.

Measurements in Flora of China

Wu, Raven & Hong (eds.). Flora of China, vol. 16 — Apocynaceae, Nerium oleander Linnaeus, Science Press (Beijing) / Missouri Botanical Garden Press / eFloras.org · www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200018424 · 2026-10-10

Flora of China records stems up to 6 m tall, very narrowly elliptic leaves 5–21 × 1–3.5 cm, sepals 3–10 mm, a purplish red, pink, white, salmon or yellow corolla, single or double, with a tube of 1.2–2.2 cm and lobes of 1.3–3 cm, and cylindric follicles 12–23 cm long. Seeds are oblong, with a coma of 0.9–1.2 cm. Seed-oil content reaches 58.5%. Flowering runs from spring to autumn.

Phenology

Flora of North America Editorial Committee (eds.). Flora of North America North of Mexico, vol. 14 — Apocynaceae, Nerium oleander Linnaeus, Flora of North America Association / eFloras.org · www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200018424 · 2026-10-10

In the United States it flowers in spring and summer and fruits from summer to fall.

Habitat and distribution

Nazimuddin & Qaiser. Flora of Pakistan — Apocynaceae, Nerium oleander Linn., University of Karachi / Missouri Botanical Garden / eFloras.org · www.efloras.org/florataxon.aspx?flora_id=5&taxon_id=200018424 · 2026-10-10

Flora of Pakistan describes the range as extending from the Mediterranean to Persia, China and Japan, common in rocky stream beds and ascending to about 5,000 ft; the species is also commonly cultivated and naturalized throughout Pakistan, where it flowers from April to October.

In North America

Flora of North America Editorial Committee (eds.). Flora of North America North of Mexico, vol. 14 — Apocynaceae, Nerium oleander Linnaeus, Flora of North America Association / eFloras.org · www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200018424 · 2026-10-10

In the United States it is introduced and grows in disturbed areas, roadsides and old homesites, at 0–600 m. It is sporadically naturalized from North Carolina to Florida and Texas, and in Arizona and California (Alabama, Arizona, California, Georgia, Louisiana, Mississippi, North Carolina, South Carolina and Texas).

In Brazil

Castello, A.C.D. Nerium in Flora e Funga do Brasil. Jardim Botânico do Rio de Janeiro — Nerium oleander L. (FB33737), Jardim Botânico do Rio de Janeiro · floradobrasil.jbrj.gov.br/FB33737 · 2026-10-10

Flora e Funga do Brasil lists Nerium oleander L. as an accepted name of exotic origin, with a shrub or tree life form, terrestrial habit, and occurrence in human-modified areas. It is recorded in 21 Brazilian states and the Federal District: AL, BA, CE, DF, ES, GO, MA, MG, MS, MT, PB, PE, PI, PR, RJ, RN, RS, SC, SE, SP and TO.

Reproductive biology

Herrera, J. (1991). The reproductive biology of a riparian Mediterranean shrub, Nerium oleander L. (Apocynaceae). Botanical Journal of the Linnean Society 106(2): 147–172, Oxford University Press / Linnean Society of London · doi.org/10.1111/j.1095-8339.1991.tb02289.x · 2026-10-10

Herrera studied two populations in southern Spain (El Garrobo and Grazalema), where the species is a sclerophyllous shrub of the banks of temporary streams. The showy, tubular flowers contain no nectar: pollination relies on insects attracted without a reward. Hand-pollinations and germination tests showed full self-compatibility, but the spatial separation of stigma and anthers prevents automatic selfing, so the plant depends on pollinators. Two years of observation yielded only eight insect visitor records.

Fruit set of open-pollinated flowers was 0.1–4.9%; hand-pollination raised it to 34–50%, indicating pollen-limited reproduction. At most four ovaries per inflorescence develop into fruit, and the author estimates that about 80% of the flowers are "excess" flowers that serve to attract pollinators. The pollen is aggregated in a sticky substance, which allows many ovules to be fertilized after a single pollination event.

Fruits are follicles with 181 seeds on average. The hairy, water-dispersed seeds are released during the rainiest season and germinate rapidly; all seedlings tracked died before completing one year, mostly from desiccation during the first summer drought.

Composition and toxicity

Bandara, Weinstein, White & Eddleston (2010). A review of the natural history, toxinology, diagnosis and clinical management of Nerium oleander (common oleander) and Thevetia peruviana (yellow oleander) poisoning. Toxicon 56(3): 273–281, Elsevier · doi.org/10.1016/j.toxicon.2010.03.026 · 2026-10-10

The review by Bandara and colleagues covers N. oleander together with yellow oleander (Thevetia peruviana). All parts of these plants are toxic and contain a variety of cardiac glycosides — those named include neriifolin, thevetin A, thevetin B and oleandrin. Ingestion of either species causes nausea, vomiting, abdominal pain, diarrhoea, dysrhythmias and hyperkalaemia, and poisoning by these plants is a common toxicological emergency in tropical and subtropical regions.

Mechanism and groups at risk

Langford & Boor (1996). Oleander toxicity: an examination of human and animal toxic exposures. Toxicology 109(1): 1–13, Elsevier · doi.org/10.1016/0300-483x(95)03296-r · 2026-10-10

Oleander cardenolides act in a way similar to the classic digitalis glycosides, inhibiting the plasma-membrane Na⁺/K⁺-ATPase, with differences in toxicity and extracardiac effects compared with digitalis. The review by Langford and Boor reports that human mortality associated with oleander ingestion is generally very low, and that small children and domestic livestock are at increased risk of poisoning.

Taxonomy: N. indicum and N. odorum

Nazimuddin & Qaiser. Flora of Pakistan — Apocynaceae, Nerium oleander Linn., University of Karachi / Missouri Botanical Garden / eFloras.org · www.efloras.org/florataxon.aspx?flora_id=5&taxon_id=200018424 · 2026-10-10

Nerium oleander L. and Nerium indicum Mill. have been treated as separate species on the basis of leaf shape, length of the connective protrusion and number of teeth of the corona appendages. Flora of Pakistan found these characters not useful for separating the two taxa and, following Grant, Fosberg and Smith (Smithsonian Contributions to Botany 17: 53, 1974, cited in the flora), treats them as conspecific. The same flora lists Nerium odorum Soland. as a synonym and gives as lectotype a cultivated specimen grown in Holland (Clifford herbarium), following Stearn.

Nomenclatural history

International Plant Names Index — Nerium oleander L., 1753, International Plant Names Index · www.ipni.org/n/urn:lsid:ipni.org:names:80460-1 · 2026-10-10

The name Nerium oleander was published by Linnaeus in Species Plantarum, page 209, in 1753 (IPNI urn:lsid:ipni.org:names:80460-1).