Oleander (Nerium oleander) is a resilient flowering shrub or small tree admired for its dense, evergreen foliage and long-lasting, showy blossoms. Originating in the Mediterranean and parts of Asia, this plant thrives in harsh conditions, including drought and poor soil, making it a favorite for landscaping in warm climates. Its ease of care and adaptability allow its vibrant clusters of pink, white, or red flowers to provide color from spring through autumn. This guide provides the practical steps necessary to grow a healthy oleander while outlining essential safety measures.
Selecting the Ideal Growing Environment
Oleander requires full, direct sun exposure for the best growth and most abundant flowering. The plant should receive a minimum of six hours of sunlight daily. Insufficient light can cause it to develop a leggy, open habit with fewer blooms. Oleander is highly tolerant of heat, making it a robust choice for sunny, exposed locations.
The shrub is not particular about soil composition and grows well even in poor or sandy soil. However, excellent drainage is required, as oleander is susceptible to root rot in waterlogged conditions. The plant naturally thrives in USDA Hardiness Zones 8 through 10, though certain cold-hardy varieties can extend this range into Zone 7b.
While mature oleander can handle brief dips in temperature, they are intolerant of temperatures consistently at or below freezing. Frost damage is a common concern in cooler growing ranges and often causes dieback on the branches. Gardeners outside of Zone 8 typically grow oleander in containers to facilitate moving the shrub indoors during winter.
Planting and Establishing Oleander
The best time to plant oleander is during the cooler periods of the year: either in early spring before new growth begins or in late summer to early fall after the main blooming period ends. When preparing the planting site, dig a hole two to three times as wide as the root ball but no deeper than the container. This wider hole allows the roots to spread easily into the surrounding soil.
Position the plant so the top of the root ball is level with or slightly above the surrounding ground, then backfill the hole with the excavated soil. If the soil is heavy clay, amending it with compost can help improve initial drainage. Immediately after planting, give the oleander a deep watering to settle the soil around the roots and eliminate air pockets.
For container growing, particularly in cooler zones, select a pot 14 to 24 inches wide with ample drainage holes. Use a quality, well-draining potting mix. Ensure the container is large enough to allow for several years of root growth before repotting. Container-grown plants require more frequent watering and attention than those established in the ground.
Routine Care and Maintenance
Watering requirements differ significantly between newly planted and established oleander. New plants need consistent moisture for the first year to develop a strong root system; water them whenever the top inch of soil feels dry. Once established, oleander is highly drought-tolerant and only requires supplemental watering during periods of extreme heat or prolonged dry spells.
Fertilizing established oleander is unnecessary unless the soil is exceptionally poor or the plant shows signs of nutrient deficiency, such as pale leaves or sparse flowering. If feeding is required, apply a balanced, slow-release granular fertilizer in early spring. Container-grown plants benefit from a regular feeding schedule, often monthly during the growing season, because nutrients leach from the potting mix.
Pruning shapes the plant and encourages more prolific blooming, as oleander flowers form on new wood. The best time for heavy pruning is in late winter or early spring, just before the start of the new growth cycle. Spent flowers can be removed (deadheaded) throughout the season to promote continued blooming and maintain a tidy appearance.
To rejuvenate an older, overgrown shrub, remove up to one-third of the oldest and thickest stems by cutting them back to the ground. Oleander is pest-resistant, but watch for common issues like scale insects, aphids, or the oleander caterpillar. These can be managed by hand-picking or by applying horticultural oil or insecticidal soap.
Gardeners in cooler climates must prepare container-grown oleander for winter by bringing them indoors before the first hard frost. After the plant finishes blooming in the fall, prune it back by about one-third of its size for easier indoor management. The plant should be placed in a cool, sheltered location that remains above freezing, and watering should be minimized until spring.
Essential Safety Precautions
All parts of the Nerium oleander plant are highly toxic due to the presence of cardiac glycosides, including oleandrin and nerium. Ingestion of any part of the plant—leaves, flowers, stems, or sap—can cause severe illness and may be fatal to humans and pets. Avoid planting oleander in areas accessible to small children or curious animals due to this toxicity.
When pruning, transplanting, or handling the plant, wear protective gear such as long sleeves, long pants, and nitrile gloves to prevent contact with the milky sap. Direct contact with the sap can cause skin irritation or dermatitis. After working with the plant, thoroughly wash all tools, hands, and exposed skin with soap and water.
Pruned material must be disposed of safely and should never be used for composting or burning. Burning oleander releases toxic fumes that can cause respiratory distress and poisoning. All cuttings should be sealed securely in plastic bags before being placed in the trash.