Oleander (Nerium oleander) is a popular ornamental shrub or small tree, frequently seen in warmer climates. This evergreen plant is admired for its abundant, often fragrant blooms and its ability to withstand drought conditions. Its attractive flowers and dense foliage make it a favored choice for landscaping, providing visual appeal and effective screening.
Understanding Oleander
Oleander is known for its dense, leathery, dark green leaves, which are typically long and narrow, 4 to 6 inches long and less than an inch wide. These leaves often grow in whorls of two or three along the woody stems. The plant’s showy flowers, typically 1 to 3 inches across, appear in clusters from early summer until mid-autumn, and sometimes year-round in very warm climates.
Flower colors range from white, pale yellow, peach, salmon, various shades of pink, and deep burgundy red. Some varieties have single or double flowers, with many double-flowered types also being fragrant. Oleander naturally grows as a mounded, rounded shrub, but it can also be trained into a small single or multi-trunked tree, reaching heights of 8 to 12 feet. This plant thrives in USDA Hardiness Zones 8 through 10.
Cultivating Oleander
Oleanders perform best in full sun, ideally at least six hours of direct sunlight, as this encourages more prolific flowering. While they can tolerate partial shade, too little light may result in a lanky growth habit and reduced bloom production. It adapts to various soil types, even poor or sandy ones, but requires well-draining soil to prevent root rot.
When planting, amend heavy or clay soils with organic matter or compost for improved drainage. Dig a hole two to three times wider than the root ball and about the same depth, ensuring the top of the root ball is level with the surrounding soil. Oleanders are drought-tolerant once established, but they benefit from occasional deep watering during dry periods to promote robust growth and flowering. Overwatering should be avoided, as it can lead to yellowing leaves or root issues.
Oleanders are not heavy feeders and often require little supplemental fertilizer. If growth appears slow, leaves are pale, or flowering is sparse, a balanced granular fertilizer, such as a 10-10-10 blend, can be applied in early spring and again in early fall. For container-grown plants, more frequent fertilization may be necessary due to nutrient leaching, every four to six weeks during the growing season. Pruning is best done in early spring, before new growth begins, as oleanders bloom on new wood. This allows for shaping, size control, or removal of cold-damaged or overgrown wood.
Oleander Toxicity and Safety Precautions
Every part of the oleander plant (Nerium oleander) is highly poisonous, containing cardiac glycosides like oleandrin and neriine, affecting the heart. This toxicity extends to humans, pets, and livestock. Ingestion of leaves, flowers, stems, or even smoke from burning the plant can be dangerous. A single leaf can be lethal to a child, and even dried plant material retains its toxicity.
Symptoms of oleander poisoning can include gastrointestinal issues like nausea, vomiting, abdominal pain, and diarrhea. Severe effects include irregular heart activity, a weak pulse, and potentially cardiac arrest. Neurological symptoms such as lethargy, dizziness, and tremors may also occur. Wear protective gloves to prevent skin irritation from the sap, and wash hands thoroughly afterward. Keep children and pets away from the plant, and dispose of pruned material carefully, avoiding burning. If exposure or ingestion is suspected, immediate medical attention or veterinary care should be sought.
Managing Common Oleander Problems
Common pests include oleander aphids and scale insects. Oleander aphids are small, yellow insects found on new growth and managed with insecticidal soap or a strong spray of water. Scale insects are small, immobile bumps on stems and leaves, addressed with horticultural oil or by gently scraping them off.
Oleander leaf scorch, a bacterial disease, causes leaves to yellow and brown, often on one side, leading to dieback. No cure exists; affected plants may need removal to prevent further spread. Fungal spots appear as discolored areas; good air circulation and avoiding overhead watering help prevent these issues. Removing affected leaves also limits spread.