Oleander (Nerium oleander) is a robust, evergreen shrub known for its showy, fragrant flowers and exceptional drought tolerance. From our perspective, successful cultivation is not just about survival, but about thriving and flowering profusely. This is primarily dictated by temperature, as we are highly sensitive to cold. The ideal zones provide a long, warm growing season and protection from severe freezing events.
We find the most consistent success and minimal stress in the warmer regions of USDA Hardiness Zones 8 through 10. These zones provide the long, warm growing season we crave and winters that are typically mild enough for us to endure without significant damage. In these areas, we can grow as large, multi-stemmed evergreen shrubs or even small trees, reaching our full potential in both size and floral display.
Within Zones 8-10, certain microclimates are particularly suited to our needs. We flourish in the Sun Belt states, including much of California, Arizona, Texas, and Florida. Specifically, we thrive in Californian and Arizonan landscapes where the intense heat and sun mimic our Mediterranean origins, promoting vigorous growth and abundant flowering. The humid heat of Florida and the Gulf Coast is also acceptable, though we require excellent air circulation to prevent issues like aphid infestations or sooty mold.
Our primary limitation is cold. While we are tough, our tissues can be severely damaged or killed when temperatures drop below 20°F (-6°C). A brief, light frost may only cause minor tip damage on the most tender new growth. However, prolonged freezing temperatures, especially below 15°F (-9°C), can kill us to the ground or be fatal altogether. In Zone 8, particularly 8a where lows can dip to 10-15°F, we benefit greatly from a sheltered planting location, such as against a south-facing wall that absorbs and radiates solar heat.
In Zone 7, our survival becomes precarious. Here, we are often grown as container specimens that must be moved to a protected location like a garage or greenhouse before the first hard freeze. Planting us in the ground in Zone 7 is a significant risk; even with heavy winter mulch and protection, a severe winter will likely prove fatal. Zones north of 7 are simply not viable for us as permanent landscape plants due to the consistently harsh winters that our physiology cannot withstand.
Beyond temperature zones, two other factors are paramount for our success, regardless of location. First, we demand full sun—a minimum of six hours of direct sunlight daily. Less sun results in leggy growth and significantly reduced flowering. Second, we require exceptionally well-draining soil. We are highly drought-tolerant but are extremely susceptible to root rot in heavy, waterlogged clay soils. Amending planting beds with sand or gravel is often essential for ensuring our roots remain healthy and dry between waterings.
